Haema Latest - haema-1.8.2+1.18.1.jar
Bewitchment latest - bewitchment-1.18-4.jar

With Haema installed you can't skip the day when sleeping in a Coffin from the Bewitchment.
Since your mod is causing an issue with that Bewitchment I have reported it here and not to them.

very rough conflict on players where it's necessary to skip days, hoping to see a fix or investigation into the cause

Bumping as I'm also currently experiencing this. It makes trying to do anything as a vampire considerably more difficult.

This interaction is unfortunately still present in v1.9.1. Sleeping in a bed skips the night and sleeping in a bewitchment coffin does not advance time at all, despite the sleep animation playing.

This issue is still present under the latest versions of both mods for 1.19.2, that being haema 1.10.4 and bewitchment 1.19-6, and is definitely on haema to fix according to bewitchment's dev.