I can confirm that this is happening also in a live version of my map where I enabled “Custom Items and Inventory”. When I pick up a Rift Point device, it always immediately drops on the ground, so it is not possible to use it at all.
A workaround for this is to add a new sub inventory for the player. The rift point device will be added to this new inventory when you pick it up and it will behave normally.
It will appear on your back, and it will appear in it’s special slot in your UI and you can drag/drop it as normal.