Relatively minor, but sometimes (not all the time) my XP gains display twice. Usually this is after a larger quest reward and I level up, and it runs through the same animation twice.
For example, if I’m 66 going on 67, I’ll see the progress bar fill up to 67, make the sound for new level, redisplay where I was at 66, fill up to 67 again, and then after that continue with the correct animation going partway into 68.
As far as I can tell the XP is adding correctly, it’s just a display issue showing the first animation twice. If it helps, I’ve never seen it repeat any other than the first level up. Meaning if I cleared a few quests at once and I go up multiple levels, it only repeats the first stage, then rolls through the rest normally.
I also think there are a few cases where I haven’t seen it display twice, but I haven’t caught on to what the difference is. I’d still say it happens 70-80% of the time I level up. It’s been going on for at least multiple weeks, possibly longer.