I've noticed, that when my bots have a large amount of items to offload to storage units, if suddenly a large shipment comes in and needs to be placed, bots will only place 6k into the memory unit, and offload the rest into other containers (Likely due to the bots only seeing 6k available in the chest).
This is especially problematic in Space Exploration if a rocket comes in off another planet. In cases where stack size is 50, with 500 slots available = up to 25k worth of items to be placed. Bots will store 6k in the main memory unit, and the other 19ish-k will be placed into other storage unit chests.