hdr + color management: gtkSwitch has transparent bars (black bars) at some fractional scales

• gtk 4.17.5
• mutter 48.rc
• gnome-shell 48.rc
• HDR monitor
• HDR enabled in gnome-control-center

gtkSwitch has transparent bars (which can appear as black or white) at some fractional scales.

I have these scales as triggered. (other scales with these resolutions aren't affected):

• 2880x1800 175%
• 2560x1600 175%, 275%, 325%
• 1920x1200 175%

node:

outset-shadow {
  blur: 2;
  outline: -1 -1 26 26 / 13;
}

The same with removed alpha, appears as black in video:

Screencast_From_2025-03-04_00-52-25-s

PXL_20250303_200117158-s

Also these bars are intermixed through the topmost windows:

PXL_20250303_210231846