Firefox lags and freezes when entering fullscreen, recovers when un-maximizing

[theduke]

When maximizing a Firefox window, the UI stutters for a bit and then becomes completely unresponsive.
Everything recovers fine after exiting fullscreen mode.

I noticed that the issue is worse in LibreWolf (a Firefox fork), which freezes immediately, while the regular Firefox stutters for a few seconds with very slow UI, and then eventually freezes.

Cosmic version: latest alpha2 , through the NixOS flake (lilyinstarlight/nixos-cosmic#335).
Kernel: 6.11
CPU/GPU: Intel 12th gen laptop CPU with integrated graphics

Potentially related issues:

• Screen Flickering [drm] *ERROR* CPU pipe A FIFO underrun: transcoder cosmic-epoch#467
• Maximising window hard freezes Cosmic #887
• Kernel 6.11 & 6.12: Minimize & maximize are delayed & maximizing the terminal freezes the session #739

[theduke]

Some extra info.
I'm seeing this in dmesg:

[ 3020.634536] i915 0000:00:02.0: [drm] *ERROR* CPU pipe A FIFO underrun: port,transcoder,