MC Version: 1.19.2
Fabric Version: 0.14.10
Mod Version: 41.0.4

Log: I don't think one is required for this type of bug as nothing seemed to appear in the log related to Regeneration when this bug occured.

Whenever you enter grace period and die in it, you don't regenerate. I'm not sure if this was an intentional change from previous versions as before when you died in grace period you would just regenerate without warning. Something to also note is that upon death, it grants me an advancement and reacts as if I have held in my regeneration for a while and have started to go critical. Hopefully you can fix this, cheers 👍 .

Just wanted to also mention, this seems to happen on Forge 1.19.2 as well.

Can I have a video of this occurring?

Sorry for the late response. Here you go for both Forge and Fabric!

Fabric: https://youtu.be/zhoTrCtdFOM

Forge: https://youtu.be/SYLcnh4Ihzo

Note: In the Forge version, the bug seems to work differently as shown in the video. You seem to be immortal in grace period until you choose to regenerate.

@HoldYourWaffle Got any idea on this? Feel like we might have missed something in the move