Windows 10 Mobile back button SHOULD NOT minimize the app, but it does.
Attach a Capx
This is an example with two layers. The back button makes the app go to the previous layout.
Attach a Visual Studio Solution
This is the VS Solution generated with C2.
Appxbundle built with C2
In order to install the app on a Windows 10 Mobile, you shoud go to "Settings", "Update & security", "For developers", "Developer mode".
Steps to Reproduce Bug
The app goes back to the previous layout then the app gets minimized.
The app should only take you to the previous layout, it SHOULD NOT minimize the app.
Operating System and Service Pack
Microsoft Lumia 435 with Windows 10 Mobile version 1703, OS Build 15063.138
Construct 2 Version ID
Release 244 (64-bits) under Windows 10 version 1703, OS Build 15063.296 and Visual Studio Professional 2015 Version 14.0.25431.01 Update 3
I have import the same C2 project on C3 R31, then exported to Windows & Xbox One (UWP), then build it with Visual Studio and it works as expected, so this has to be a C2 bug.
This is the VS Solution generated with C3.
Appxbundle built with C3
I can't reproduce either on an emulator, or with Windows 10 itself (add the Windows Store object and you can set a back button visible in the caption, and use that to trigger 'On back'). It works correctly as far as I can see. I don't have hardware to test on right now, but will try to get a real device to double-check on.
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Oh, noticed you used a minified export and that caused the issue, it only happened when minifying. Should be fixed in the next build.