All items in an EVA inventory slot get lost when one of them is placed on ground.
My example here uses the Work Lamp part but I assume it happens with other inventory items as well.
Start with two Work Lamps in EVA inventory, stored in a single slot. (It must be a stack of 2 items in one slot - not two different slots of 1 each.)
Place the Work Lamp on the ground.
You now have zero Work Lamps left in inventory. Even though there were two in the slot and you only put one of them down.
It seems as if placing an EVA inventory item on the ground deletes the entire stack from inventory when it should just subtract 1 from the stack count and only delete the stack if that makes the count become zero.