I sometimes experience dupes working on a hydronfan not going to sleep, when the night starts. Ironically this has no effect on the status "Interrupted sleep"
But all other activities like eating or going to the lavatory seem to work properly while working on the hydrofan.
Unfortunatly I do not know how to reproduce this bug
Steps to Reproduce
Just put dupes working on hydrofans and wait for it to become night
This issue has not been confirmed by a developer yet.