When I upgrade Cart Assembler by using upgrade module, if I quit and then go back to this world, it will change type.
To reproduce:

1. Give your own Cart Assembler and any upgrade module (in this case I use Upgrade: Creative)
2. Sneak + right click upgrade module into the Cart Assembler.
   
3. Quit game and then re-open this saved world.
4. The Upgrade: Creative has been changed to Upgrade: Batteries.
   
5. If I break Upgrade: Batteries and Cart Assembler, after that place Cart Assembler at the same location, it have Upgrade: Power Crystal.
   
6. Quit game and then re-open this saved world. Now Upgrade: Power Crystal has gone.