There's a few inventory glitches I've had. But the worse, beside the constant and intense lag, is this glitch with any random slot that prevent me from putting things there.

The game will occasionally act as though there's an object in an inventory slot, not letting me place anything there. If I press Y to transfer it from perhaps the top of my inventory, to this (glitched spot) on the hotbar, it will appear in the glitched spot for a second, and then teleport back to its original spot. I can't pick up items from the ground when this happens; the same teleport thing happens from chests or workbenches. 

It will fix itself after a minute or so, and will glitch out on another spot a little time later. It happens at random it seems: Sometimes a slot will get glitched after moving something out of it; sometimes when trying to put something into it after it was empty for some time. I've had this  while playing in my realm, but also in my own survival worlds and creative worlds.

I do suppose the inventories are also very laggy; items take time to move, everything just feels like it's delayed.