diff --git a/ReactNativeClient/lib/WebDavApi.js b/ReactNativeClient/lib/WebDavApi.js
index 84f13c180..5752aef75 100644
--- a/ReactNativeClient/lib/WebDavApi.js
+++ b/ReactNativeClient/lib/WebDavApi.js
@@ -161,6 +161,8 @@ class WebDavApi {
 
 		let response = null;
 
+		// console.info('WebDAV', method + ' ' + path, headers, options);
+
 		if (options.source == 'file' && (method == 'POST' || method == 'PUT')) {
 			response = await shim.uploadBlob(url, fetchOptions);
 		} else if (options.target == 'string') {
diff --git a/ReactNativeClient/lib/file-api-driver-webdav.js b/ReactNativeClient/lib/file-api-driver-webdav.js
index 460d70ae1..a42a7f555 100644
--- a/ReactNativeClient/lib/file-api-driver-webdav.js
+++ b/ReactNativeClient/lib/file-api-driver-webdav.js
@@ -4,6 +4,8 @@ const { basicDelta } = require('lib/file-api');
 const { rtrimSlashes, ltrimSlashes } = require('lib/path-utils.js');
 const Entities = require('html-entities').AllHtmlEntities;
 const html_entity_decode = (new Entities()).decode;
+const { shim } = require('lib/shim');
+const { basename } = require('lib/path-utils');
 
 class FileApiDriverWebDav { 
 
@@ -20,6 +22,7 @@ class FileApiDriverWebDav {
 			const result = await this.api().execPropFind(path, 0, [
 				'd:getlastmodified',
 				'd:resourcetype',
+				'd:getcontentlength', // Remove this once PUT call issue is sorted out
 			]);
 
 			const resource = this.api().objectFromJson(result, ['d:multistatus', 'd:response', 0]);
@@ -34,6 +37,9 @@ class FileApiDriverWebDav {
 		const isCollection = this.api().stringFromJson(resource, ['d:propstat', 0, 'd:prop', 0, 'd:resourcetype', 0, 'd:collection', 0]);
 		const lastModifiedString = this.api().stringFromJson(resource, ['d:propstat', 0, 'd:prop', 0, 'd:getlastmodified', 0]);
 
+		const sizeDONOTUSE = Number(this.api().stringFromJson(resource, ['d:propstat', 0, 'd:prop', 0, 'd:getcontentlength', 0]));
+		if (isNaN(sizeDONOTUSE)) throw new Error('Cannot get content size: ' + JSON.stringify(resource));
+
 		if (!lastModifiedString) throw new Error('Could not get lastModified date: ' + JSON.stringify(resource));
 
 		const lastModifiedDate = new Date(lastModifiedString);
@@ -44,6 +50,7 @@ class FileApiDriverWebDav {
 			created_time: lastModifiedDate.getTime(),
 			updated_time: lastModifiedDate.getTime(),
 			isDir: isCollection === '',
+			sizeDONOTUSE: sizeDONOTUSE, // This property is used only for the WebDAV PUT hack (see below) so mark it as such so that it can be removed with the hack later on.
 		};
 	}
 
@@ -229,7 +236,32 @@ class FileApiDriverWebDav {
 	}
 
 	async put(path, content, options = null) {
-		await this.api().exec('PUT', path, content, null, options);
+		// In theory, if a client doesn't complete an upload, the file will not appear in the Nextcloud app. Likewise if
+		// the server interrupts the upload midway, the client should receive some kind of error and try uploading the
+		// file again next time. At the very least the file should not appear half-uploaded on the server. In practice
+		// however it seems some files might end up half uploaded on the server (at least on ocloud.de) so, for now,
+		// instead of doing a simple PUT, we do it to a temp file on Nextcloud, then check the file size and, if it
+		// matches, move it its actual place (hoping the server won't mess up and only copy half of the file).
+		// This is innefficient so once the bug is better understood it should hopefully be possible to go back to
+		// using a single PUT call.
+
+		let contentSize = 0;
+		if (content) contentSize = content.length;
+		if (options && options.path) {
+			const stat = await shim.fsDriver().stat(options.path);
+			contentSize = stat.size;
+		}
+
+		const tempPath = this.fileApi_.tempDirName() + '/' + basename(path) + '_' + Date.now();
+		await this.api().exec('PUT', tempPath, content, null, options);
+
+		const stat = await this.stat(tempPath);
+		if (stat.sizeDONOTUSE != contentSize) {
+			// await this.delete(tempPath);
+			throw new Error('WebDAV PUT - Size check failed for ' + tempPath + ' Expected: ' + contentSize + '. Found: ' + stat.sizeDONOTUSE);
+		}
+
+		await this.move(tempPath, path);
 	}
 
 	async delete(path) {
@@ -241,7 +273,9 @@ class FileApiDriverWebDav {
 	}
 
 	async move(oldPath, newPath) {
-		throw new Error('Not implemented');
+		await this.api().exec('MOVE', oldPath, null, {
+			'Destination': this.api().baseUrl() + '/' + newPath,
+		});
 	}
 
 	format() {
diff --git a/ReactNativeClient/lib/file-api.js b/ReactNativeClient/lib/file-api.js
index 5ec29fe7b..0ed87dcbe 100644
--- a/ReactNativeClient/lib/file-api.js
+++ b/ReactNativeClient/lib/file-api.js
@@ -12,6 +12,17 @@ class FileApi {
 		this.driver_ = driver;
 		this.logger_ = new Logger();
 		this.syncTargetId_ = null;
+		this.tempDirName_ = null;
+		this.driver_.fileApi_ = this;
+	}
+
+	tempDirName() {
+		if (this.tempDirName_ === null) throw Error('Temp dir not set!');
+		return this.tempDirName_;
+	}
+
+	setTempDirName(v) {
+		this.tempDirName_ = v;
 	}
 
 	fsDriver() {
@@ -40,9 +51,10 @@ class FileApi {
 	}
 
 	fullPath_(path) {
-		let output = this.baseDir_;
-		if (path != '') output += '/' + path;
-		return output;
+		let output = [];
+		if (this.baseDir_) output.push(this.baseDir_);
+		if (path) output.push(path);
+		return output.join('/');
 	}
 
 	// DRIVER MUST RETURN PATHS RELATIVE TO `path`
diff --git a/ReactNativeClient/lib/synchronizer.js b/ReactNativeClient/lib/synchronizer.js
index 743f889b5..f2d9d0359 100644
--- a/ReactNativeClient/lib/synchronizer.js
+++ b/ReactNativeClient/lib/synchronizer.js
@@ -18,7 +18,7 @@ class Synchronizer {
 		this.state_ = 'idle';
 		this.db_ = db;
 		this.api_ = api;
-		//this.syncDirName_ = '.sync';
+		this.syncDirName_ = '.sync';
 		this.resourceDirName_ = '.resource';
 		this.logger_ = new Logger();
 		this.appType_ = appType;
@@ -195,7 +195,8 @@ class Synchronizer {
 		this.logSyncOperation('starting', null, null, 'Starting synchronisation to target ' + syncTargetId + '... [' + synchronizationId + ']');
 
 		try {
-			//await this.api().mkdir(this.syncDirName_);
+			await this.api().mkdir(this.syncDirName_);
+			this.api().setTempDirName(this.syncDirName_);
 			await this.api().mkdir(this.resourceDirName_);
 
 			let donePaths = [];