I remember way back that if sims had bed woohoo before they were due to go to sleep for the night, they would automatically stay in bed and sleep.
Similar to this thread (which is marked as fixed):
Sims in Romantic Relationship Keep Getting Out of Bed/Do not sleep in bed | EA Forums - 4972711
My sims are tired and ready for the nights sleep, but woohoo first. They stay in bed and the zzz's are coming out of their heads but they are not actually asleep (no greyed portrait, no energy rise). I have to click on the bed to select sleep, the sim then gets back out of bed to get back into bed to go to sleep. Sometimes it affects one sim, sometimes both.
Playing on PC, Windows 11, No mods or CC, all packs installed except about three kits.