Disposition drops after persuasion sessions
This is on Windows 11 with a very recent dev build. If you repeatedly persuade (e.g. admire) an NPC until their disposition hits/exceeds 100 at least once (sometimes twice) during the conversation, then exit the conversation, the next time you speak with the NPC, their disposition will be at least a couple points lower (and sometimes significantly lower, especially after longer sessions where disposition hits 100 several times during the conversation) than what it had been at the end of the prior conversation. I encountered this when spamming persuasion in order to build my speechcraft skill, so the conversations where this became an issue usually lasted through at least a few dozen persuasion attempts; however, the only trigger seems to be exceeding 100 disposition at one or more points during the conversation, rather than a particular or large number of persuasion attempts in general.
I suspect something is going on with changes above 100 that you can't "see" in the disposition bar during the first conversation that are only properly adjusted for after the first conversation ends, but I'm sure the devs will be able to see what's up.