If somehow a request gets fulfilled while a requester robot has picked up an item, the item will be dropped.

I had a picker that I changed filter. It immediately went to a drop off location to get rid of the now invalid items. Is something like that possible with the requester too?

Are you sure there was a valid drop point in the robot's working area, that wasn't occupied?, the delivery bot should only drop items to the ground if it doesn't find anywhere to put them.

Oops. My bad.