>>I get random behaviour from UT about replies to my posts. Some of them appear and some don't, even after a global refresh. As an exemple, message #726948 never appeared in my replies section.
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>I sometimes get a "late" advice of replies to my messages. I've noticed that if I click on the top "New messages..." icon or the number beside it, I will see the message in the list yet have no indication in the "Replies". However, when the next 'refresh cycle' is done, I then get notice of the message (even if I already replied to it).

This is normal. The audio notification is recorded and will kick in as a precaution mechanism.