There's a bug that allows you to turn storage downgrades into every storage up (aside from the creative ones).

To reproduce the bug get a drawer and fill it with over one stack of material into a drawer
Add any storage upgrade one through five and a storage downgrade
Shift right click the drawer to open the upgrade interface of the drawer
Click the storage downgrade to pick it up out of the drawer then click on the storage upgrade while holding the storage downgrade
Then click the storage upgrade again

Quick video for demonstration if necessary: https://www.youtube.com/watch?v=29vQarDCsrs