I did some testing on the moonlight-lag problem today.
The lag/stutter only happens if you have your "Books extra-inventory" selected.
Changing to "Upgrades", "Stones" or "Chests" will always fix the problem.
Whenever you do a relog, your selected extra-inventory will automatically change back to "Books", so you'll have to do the fix again.
Next I tested if the problem is that moonlight chests are moved into this inventory by quest. That wasn't the problem.
Throwing some moonlight chests on the ground and then picking them up does also create lag/sutter. (if "Books" inventory is selected)
Finally I tested if it happens with other chests too. This doesn't seem to be the case, although I didn't test every single chest available in the game.
So far the problem only happens with the moonlight-chests.