If you are on a quest that requires a certain number of scarabs and idols collected in AQ, and someone trades scarabs to you that you did not directly loot, it removes all or some of them from the quest tracker, even though you now have more than you did before.
For example, quest will show 5/5 crystal scarabs tracked towards the quest, alt account trades additional crystal scarabs to my main, then the count on the quest tracker may go down to 3/5 or 0/5 crystal scarabs. I have to trade the whole stack of scarabs back to the alt character then back to the main to get the quest numbers to repopulate. Reloading didn’t seem to help.
I don’t think taking them from the mail caused this issue, but I would have to test again to be sure.
Editing to add: idols can be similarly affected.