After having a nightmare you are not able to use the bed again even after breaking it and putting it back again. you get the "cannot sleep now there are monsters around". but if you use another bed close by or pick up and move the bed a certain distance you can sleep again

This is a vanilla mechanic. If there are nearby hostile mobs you wont be able to sleep.

I am having the same issue. Even without there being any hostile mobs around.

I've even used a mega torch and the only mobs around are sprouts from roots 2 and a snow dragon from dragon mounts 2 which both have been around while I have been able to sleep normally.

how do nightmares even work? are they dimensions?