Also not see it on kill 10 somethings unless they gave items. Well I don't believe it will make it worse. So. That's why it's a suggestion to devs they'd be the ones who would possibly know about problems.
Now that red error I have seen. But it's been 100% of the time when completeing a RoE that gives an item and the message even says that. It then stops you from getting any credit until you clear invent enough and manually accept completion. Very commonly seen with time limit ones xp one in particular. And sometimes your invent isn't full per se but was temporarily full at the time before it sorted as happens a lot when cleaving (even lose items that way sometimes sadly)