diff --git a/maps/chronosphere/terrain_specials.lua b/maps/chronosphere/terrain_specials.lua
index 7270eeb9..8fe1bdbe 100644
--- a/maps/chronosphere/terrain_specials.lua
+++ b/maps/chronosphere/terrain_specials.lua
@@ -75,7 +75,7 @@ function Public_terrain.fish_market(surface, left_top)
     alignment = "center",
     scale_with_zoom = false
   }
-  local fishchest = surface.create_entity({name = "compilatron-chest", force = "player", position = {x = left_top.x + 11, y = left_top.y + 16}})
+  local fishchest = surface.create_entity({name = "steel-chest", force = "player", position = {x = left_top.x + 11, y = left_top.y + 16}})
   fishchest.destructible = false
   fishchest.minable = false
   fishchest.operable = false
diff --git a/maps/chronosphere/upgrades.lua b/maps/chronosphere/upgrades.lua
index d77f22b4..067cbe75 100644
--- a/maps/chronosphere/upgrades.lua
+++ b/maps/chronosphere/upgrades.lua
@@ -157,7 +157,7 @@ end
 local function mk2_buy()
   local objective = Chrono_table.get_table()
   if objective.upgradechest[13] and objective.upgradechest[13].valid then
-	local inv = objective.upgradechest[14].get_inventory(defines.inventory.chest)
+	local inv = objective.upgradechest[13].get_inventory(defines.inventory.chest)
     inv.insert({name = "power-armor-mk2", count = 1})
   end
 end
diff --git a/modules/wave_defense/main.lua b/modules/wave_defense/main.lua
index b54c2e97..304bc22d 100644
--- a/modules/wave_defense/main.lua
+++ b/modules/wave_defense/main.lua
@@ -236,6 +236,27 @@ local function set_next_wave()
 	wave_defense_table.next_wave = game.tick + wave_defense_table.wave_interval
 end
 
+local function reform_group(group)
+	local wave_defense_table = WD.get_table()
+	local group_position = {x = group.position.x, y = group.position.y}
+	local step_length = wave_defense_table.unit_group_command_step_length
+	local position = group.surface.find_non_colliding_position("biter-spawner", group_position, step_length, 4)
+	if position then
+		local new_group = group.surface.create_unit_group{position = position, force = group.force}
+		for key, biter in pairs(group.members) do
+			new_group.add_member(biter)
+		end
+		debug_print("Creating new unit group, because old one was stuck.")
+		table_insert(wave_defense_table.unit_groups, new_group)
+		return new_group
+	else
+		debug_print("Destroying stuck group.")
+		--table.remove(wave_defense_table.unit_groups, group) --need group id instead to work, so as of now, groups are removed only by regular remove checks :( !
+		group.destroy()
+	end
+	return nil
+end
+
 local function get_commmands(group)
 	local wave_defense_table = WD.get_table()
 	local commands = {}
@@ -374,6 +395,11 @@ local function command_unit_group(group)
 	if wave_defense_table.unit_group_last_command[group.group_number] then
 		if wave_defense_table.unit_group_last_command[group.group_number] + wave_defense_table.unit_group_command_delay > game.tick then return end
 	end
+	local tile = group.surface.get_tile(group.position)
+	if tile.valid and tile.collides_with("player-layer") then
+		group = reform_group(group)
+	end
+	if not group then return end
 
 	group.set_command({
 		type = defines.command.compound,