Klwp v3.43
Steps to recreate:
1. Use an image as background
2. Add a shape in root
3. Add the "Blurred background" mask to said shape
4. Increase blur value to anything above 0
Result: https://gfycat.com/vibrantpopularlangur
The issue is only present in editor, doesn't affect the home screen, but is extremely annoying when you want to work on your preset.