Can be observed with Process Monitor with the following steps:

1. Place a .kra file on a directory that does not contain the Krita install to be started (using `C:\Users\Alvin\Desktop` here)
2. Start Process Monitor, add filters:
  - Process Name is `krita.exe`
  - Path contains `C:\Users\Alvin\Desktop`
3. Double-click on the .kra file to start Krita (make sure Krita isn't already opened or that multiple instances are allowed
4. You should see a bunch of failed file open attempts in Process Monitor with "bundle:" in the path

A bunch of them look like `C:\Users\Alvin\Desktop\bundle:\C:\Program Files\Krita (x64)\share\krita\bundles\Krita_4_Default_Resources.bundle:brushes\abominable_snowman.png`. The most probable cause would be some code treating the path as real filesystem paths (processed with Qt's file-related functions) and causing a forward slash to become a backward slash.

<boud> um
<boud> bundle:\ looks really weird
<boud> krita checks for bundle:/ to see if something is part of a bundle