If theres a way to fix it would be great.

I've highlighted the areas in red that should be container space but for some reason they wont allow items to place. Which makes storage in specific containers unfavorable unless its for a handful of items or bulk of which you do not wish to organize. I also include the backpack in the picture to show how containers should be which you know. There may be reasons why they aren't like the backpack that you are aware of and cannot fix.
But just in case I wanted to bring this to your attention.

I've just found out that if you place items in either container icon rather then opening it up and placing it manually, items will place in those red selected areas automatically. It's when you manually try to place items in those spots that it will not let you.