Vacillating loyalty

[Gilrandir]

End-turn stuff off the top of my head:

• You can get an event that will lower happiness or destroy buildings that have a happiness effect.
• An AI faction can move spies into your province to kick up unrest.
• Depending on the religious mix in a province, an AI faction's proselytizer can stir up trouble.
• Something untoward can happen to your faction leader or governor.

I try to keep happiness above 120%. This gives me a little wiggle room for the unexpected, and also prevents re-emergences from dragging in my provinces. Don't know why you would see unexplained shifts before hitting end-turn though. Are ships (and the moving thereof) involved?

I can't say I was too observant to notice all of the things you think might be the reason. Certainly not events that influence happiness or destruction of buildings are involved. No trouble with faction leader. Not sure about religious agents or spies (you can't see others than your own). Not sure about the ships either, but I believe not, as it may equally happen to inland provinces without a sea coast. But all these things can influence the loyalty AFTER you end your turn, not DURING the same turn.