[reg: 5.5.1 => 5.6.0rc] Fast blur not working correctly

Hello,

Yesterday I finally downloaded 5.6.0 RC and found that that for some weird reason the app's "blur panel" wasn't working correctly. I will attach the screenshots for a better idea of what I'm talking about, with a minimal case test.

The one with the whole black background covered is the result of the app compiled against 5.6.0 RC. The one with the translucent panel is the app compiled against 5.5.1.

I've tested it against android (emulator and device), and desktop (Linux environment, check Environment details)