Steps to reproduce:
1- Go to options menu.
2- Activate "touchscreen mode"
3- Try to move an item in your inventory.
3.1- RMB and LMB doesn't works fine. If you put your mouse in the up part of a inventory slots, it put one item down. You can put another one in the same spot.

Sorry

• For my bad english.
  I'm brazilian, if some mod can edit this to fix grammar, i will be happy =]

• If this was alredy reported.
  I serached for "Touch Screen" but i didn't found nothing.