The attached picture shows the inventory as it looks when it is filled. The giant blank space on the bottom right is an example of the idea that the 252 total slots are there, but not visible. That item is a gas can, whose top area I dragged over the bottom of the inventory and placed. The smaller one on the left is a medkit undergoing the same issue.
I tested this with non-storage related items such as weapons and they too lost their image and disappeared after restart.
My recommendation to fix the issue would be to allow for a scrollable inventory to allow the other items to "exist" in the tent.