When this is reported, it's usually that you are clicking the "finish quest" button before all the items make it into your inventory. This tends to happen if you're buying the items and clicking to finish the quest really fast. If you're buying the items from Shop Search, it may take a second for the purchase to complete.

Hm, thanks for clarifying. That's definitely a problem, then. The next time it happens, could you please let me know which quest it was and what specific items were asked for? And I will take a closer look.

What happens when you submit the Oracle quest? Do you get an error message?