I hope I'm not that late. The glue used to bind the Protank is Silicone, water based, and easily attacked by glicerin. I rebuilt mine with a clear hot glue gun. Make sure to clean everything thoroughly with acetone, make sure it's bone dry, and apply a thin layer of the hot melt on the top of the glass. Put back and keep it pressed for a few minutes until it dries. Screwing and unscrewing is not the issue here, it's bonded with the wrong glue. You can use superglue too, but hot melt will last longer and dry faster.