I have noticed issues with versions V388.0.21.51 and beyond. While flying around places like Rano and Courcle, the game will freeze up for a second, every 3 or 4 seconds. After a bit of trial and error I narrowed this down to UOTiara's modded maps. Prior to V388.0.21.51 I didn't have this issue, sadly V388.0.21.50's Abyss does not seem to load some things correctly anymore, specifically the map modifications.
EDIT: I would post a log, but even after turning all the logging options on I only seem to get patching log, which isn't showing any errors.