Uninstalled through deactivating them by mod manager or fully remove them?
There's several mods related to magic mirror and character apparence that will make it stop working (or better said make just what you describe) after update just for being present in the mod folder or overridden games file even when they are deactivated.
If that the case your options are:
-Live without magic mirror until all the mod are update
-Fully unsintall apparence and CC mods until they are update
-The one that i personally recommended, revert to previous patch until all your mods are update. Basically if your are making a modded playthrough you should refrain from update the game before the mods
Thanks for the advice. I did fully remove the mods, but it didn't help. I even started a fresh game in case it was a save game issue.
I then found out that it actually is not an issue of not working at all, but that there is a delay of about a minute from pressing the confirm button. So the mirror works, but I have to wait a minute to get back to the game.