diff --git a/CliClient/tests/synchronizer.js b/CliClient/tests/synchronizer.js
index e86da2c79..fe560f2b1 100644
--- a/CliClient/tests/synchronizer.js
+++ b/CliClient/tests/synchronizer.js
@@ -683,12 +683,12 @@ describe('Synchronizer', function() {
 
 		await switchClient(2);
 
-		synchronizer().debugFlags_ = ['cancelDeltaLoop2'];		
+		synchronizer().testingHooks_ = ['cancelDeltaLoop2'];		
 		let context = await synchronizer().start();
 		let notes = await Note.all();
 		expect(notes.length).toBe(0);
 
-		synchronizer().debugFlags_ = [];
+		synchronizer().testingHooks_ = [];
 		await synchronizer().start({ context: context });
 		notes = await Note.all();
 		expect(notes.length).toBe(1);
@@ -702,9 +702,9 @@ describe('Synchronizer', function() {
 		let disabledItems = await BaseItem.syncDisabledItems(syncTargetId());
 		expect(disabledItems.length).toBe(0);
 		await Note.save({ id: noteId, title: "un mod", });
-		synchronizer().debugFlags_ = ['rejectedByTarget'];
+		synchronizer().testingHooks_ = ['rejectedByTarget'];
 		await synchronizer().start();
-		synchronizer().debugFlags_ = [];
+		synchronizer().testingHooks_ = [];
 		await synchronizer().start(); // Another sync to check that this item is now excluded from sync
 
 		await switchClient(2);
diff --git a/ElectronClient/app/gui/EncryptionConfigScreen.jsx b/ElectronClient/app/gui/EncryptionConfigScreen.jsx
index 6512d9c17..db4d5afd5 100644
--- a/ElectronClient/app/gui/EncryptionConfigScreen.jsx
+++ b/ElectronClient/app/gui/EncryptionConfigScreen.jsx
@@ -121,7 +121,7 @@ class EncryptionConfigScreenComponent extends React.Component {
 			}
 		}
 
-		const decryptedItemsInfo = this.props.encryptionEnabled ? <p style={theme.textStyle}>{shared.decryptedStatText(this)}</p> : null;
+		const decryptedItemsInfo = <p style={theme.textStyle}>{shared.decryptedStatText(this)}</p>;
 		const toggleButton = <button onClick={() => { onToggleButtonClick() }}>{this.props.encryptionEnabled ? _('Disable encryption') : _('Enable encryption')}</button>
 
 		let masterKeySection = null;
diff --git a/ElectronClient/app/main-html.js b/ElectronClient/app/main-html.js
index 0cbe3e673..3a15d4ef7 100644
--- a/ElectronClient/app/main-html.js
+++ b/ElectronClient/app/main-html.js
@@ -3,6 +3,15 @@
 // Make it possible to require("/lib/...") without specifying full path
 require('app-module-path').addPath(__dirname);
 
+// Disable React message in console "Download the React DevTools for a better development experience"
+// https://stackoverflow.com/questions/42196819/disable-hide-download-the-react-devtools#42196820
+__REACT_DEVTOOLS_GLOBAL_HOOK__ = {
+	supportsFiber: true,
+	inject: function() {},
+	onCommitFiberRoot: function() {},
+	onCommitFiberUnmount: function() {},
+};
+
 const { app } = require('./app.js');
 const Folder = require('lib/models/Folder.js');
 const Resource = require('lib/models/Resource.js');
diff --git a/ReactNativeClient/lib/MdToHtml.js b/ReactNativeClient/lib/MdToHtml.js
index fd633f831..7510e0747 100644
--- a/ReactNativeClient/lib/MdToHtml.js
+++ b/ReactNativeClient/lib/MdToHtml.js
@@ -73,7 +73,7 @@ class MdToHtml {
 
 	renderImage_(attrs, options) {
 		const loadResource = async (id) => {
-			console.info('Loading resource: ' + id);
+			// console.info('Loading resource: ' + id);
 
 			// Initially set to to an empty object to make
 			// it clear that it is being loaded. Otherwise
diff --git a/ReactNativeClient/lib/file-api.js b/ReactNativeClient/lib/file-api.js
index 67d32d4df..ebb387686 100644
--- a/ReactNativeClient/lib/file-api.js
+++ b/ReactNativeClient/lib/file-api.js
@@ -1,5 +1,7 @@
 const { isHidden } = require('lib/path-utils.js');
 const { Logger } = require('lib/logger.js');
+const { shim } = require('lib/shim');
+const JoplinError = require('lib/JoplinError');
 
 class FileApi {
 
@@ -10,6 +12,10 @@ class FileApi {
 		this.syncTargetId_ = null;
 	}
 
+	fsDriver() {
+		return shim.fsDriver();
+	}
+
 	driver() {
 		return this.driver_;
 	}
@@ -83,8 +89,13 @@ class FileApi {
 		return this.driver_.get(this.fullPath_(path), options);
 	}
 
-	put(path, content, options = null) {
-		this.logger().debug('put ' + this.fullPath_(path));
+	async put(path, content, options = null) {
+		this.logger().debug('put ' + this.fullPath_(path), options);
+		
+		if (options && options.source === 'file') {
+			if (!await this.fsDriver().exists(options.path)) throw new JoplinError('File not found: ' + options.path, 'fileNotFound');
+		}
+
 		return this.driver_.put(this.fullPath_(path), content, options);
 	}
 
diff --git a/ReactNativeClient/lib/shim-init-node.js b/ReactNativeClient/lib/shim-init-node.js
index 04861d594..6c8f4766e 100644
--- a/ReactNativeClient/lib/shim-init-node.js
+++ b/ReactNativeClient/lib/shim-init-node.js
@@ -4,14 +4,20 @@ const { GeolocationNode } = require('lib/geolocation-node.js');
 const { FileApiDriverLocal } = require('lib/file-api-driver-local.js');
 const { time } = require('lib/time-utils.js');
 const { setLocale, defaultLocale, closestSupportedLocale } = require('lib/locale.js');
+const { FsDriverNode } = require('lib/fs-driver-node.js');
 
 function shimInit() {
-	shim.fs = fs;
+	shim.fsDriver = () => { throw new Error('Not implemented') }
 	shim.FileApiDriverLocal = FileApiDriverLocal;
 	shim.Geolocation = GeolocationNode;
 	shim.FormData = require('form-data');
 	shim.sjclModule = require('lib/vendor/sjcl.js');
 
+	shim.fsDriver = () => {
+		if (!shim.fsDriver_) shim.fsDriver_ = new FsDriverNode();
+		return shim.fsDriver_;
+	}
+
 	shim.randomBytes = async (count) => {
 		const buffer = require('crypto').randomBytes(count);
 		return Array.from(buffer);
diff --git a/ReactNativeClient/lib/shim-init-react.js b/ReactNativeClient/lib/shim-init-react.js
index c2f9590cd..695c8221d 100644
--- a/ReactNativeClient/lib/shim-init-react.js
+++ b/ReactNativeClient/lib/shim-init-react.js
@@ -3,6 +3,7 @@ const { GeolocationReact } = require('lib/geolocation-react.js');
 const { PoorManIntervals } = require('lib/poor-man-intervals.js');
 const RNFetchBlob = require('react-native-fetch-blob').default;
 const { generateSecureRandom }  = require('react-native-securerandom');
+const FsDriverRN = require('lib/fs-driver-rn.js').FsDriverRN;
 
 function shimInit() {
 	shim.Geolocation = GeolocationReact;
@@ -10,6 +11,11 @@ function shimInit() {
 	shim.clearInterval = PoorManIntervals.clearInterval;
 	shim.sjclModule = require('lib/vendor/sjcl-rn.js');
 
+	shim.fsDriver = () => {
+		if (!shim.fsDriver_) shim.fsDriver_ = new FsDriverRN();
+		return shim.fsDriver_;
+	}
+
 	shim.randomBytes = async (count) => {
 		const randomBytes = await generateSecureRandom(count);
 		let temp = [];
diff --git a/ReactNativeClient/lib/shim.js b/ReactNativeClient/lib/shim.js
index 931763911..11990a267 100644
--- a/ReactNativeClient/lib/shim.js
+++ b/ReactNativeClient/lib/shim.js
@@ -107,7 +107,7 @@ shim.fetchWithRetry = async function(fetchFn, options = null) {
 shim.nativeFetch_ = typeof fetch !== 'undefined' ? fetch : null;
 shim.fetch = () => { throw new Error('Not implemented'); }
 shim.FormData = typeof FormData !== 'undefined' ? FormData : null;
-shim.fs = null;
+shim.fsDriver = () => { throw new Error('Not implemented') }
 shim.FileApiDriverLocal = null;
 shim.readLocalFileBase64 = (path) => { throw new Error('Not implemented'); }
 shim.uploadBlob = () => { throw new Error('Not implemented'); }
diff --git a/ReactNativeClient/lib/synchronizer.js b/ReactNativeClient/lib/synchronizer.js
index 24fc0a67a..62b42a285 100644
--- a/ReactNativeClient/lib/synchronizer.js
+++ b/ReactNativeClient/lib/synchronizer.js
@@ -10,7 +10,7 @@ const { time } = require('lib/time-utils.js');
 const { Logger } = require('lib/logger.js');
 const { _ } = require('lib/locale.js');
 const { shim } = require('lib/shim.js');
-const moment = require('moment');
+const JoplinError = require('lib/JoplinError');
 
 class Synchronizer {
 
@@ -27,7 +27,7 @@ class Synchronizer {
 
 		// Debug flags are used to test certain hard-to-test conditions
 		// such as cancelling in the middle of a loop.
-		this.debugFlags_ = [];
+		this.testingHooks_ = [];
 
 		this.onProgress_ = function(s) {};
 		this.progressReport_ = {};
@@ -279,7 +279,7 @@ class Synchronizer {
 							const localResourceContentPath = result.path;
 							await this.api().put(remoteContentPath, null, { path: localResourceContentPath, source: 'file' });
 						} catch (error) {
-							if (error && error.code === 'rejectedByTarget') {
+							if (error && ['rejectedByTarget', 'fileNotFound'].indexOf(error.code) >= 0) {
 								await handleCannotSyncItem(syncTargetId, local, error.message);
 								action = null;
 							} else {
@@ -303,11 +303,7 @@ class Synchronizer {
 
 						let canSync = true;
 						try {
-							if (this.debugFlags_.indexOf('rejectedByTarget') >= 0) {
-								const error = new Error('Testing rejectedByTarget');
-								error.code = 'rejectedByTarget';
-								throw error;
-							}
+							if (this.testingHooks_.indexOf('rejectedByTarget') >= 0) throw new JoplinError('Testing rejectedByTarget', 'rejectedByTarget');
 							const content = await ItemClass.serializeForSync(local);
 							await this.api().put(path, content);
 						} catch (error) {
@@ -449,7 +445,7 @@ class Synchronizer {
 				this.logSyncOperation('fetchingTotal', null, null, 'Fetching delta items from sync target', remotes.length);
 
 				for (let i = 0; i < remotes.length; i++) {
-					if (this.cancelling() || this.debugFlags_.indexOf('cancelDeltaLoop2') >= 0) {
+					if (this.cancelling() || this.testingHooks_.indexOf('cancelDeltaLoop2') >= 0) {
 						hasCancelled = true;
 						break;
 					}