Hello!
I couldn't reproduce the bug anymore after the hotfix (neither with releasing the prisoners normally or after battles, in town or castle dungeons etc where it worked beforehand) however I started noticing that the conformity resets for top tier units after the latest hotfix.
If I, for example, have a a stack of 10 Battanian Fian Champions and 5 are recruitable from the prisoners, and I win a battle afterward and capture 4 new Fian Champion, the 5 recruitable will be reset to 0 and the conformity level will start from 0 again.
Only works for top tier units (saw same behavior for Imperial Cataphracts, Banner Knights)