When doing activities, there is occasionally a noticeable lag or delay from using the buttons to start/end a lap or set, or tuning on the watch interface / screen.
This can be done at random times either during an activity (running or strength), or when the watch is just in Smart mode.
This is pretty debilitating as I can't tell if the watch has died or if it's just being unresponsive.
Currently on 11.28, but I believe this was noticeable since the last stable/first or second beta release.