Are you sure it is a bug?
1 - Paratroopers can only drop on enemy land. They cannot use the transports to redeploy. With the paratroopers loaded the transport does not have the option to repeploy.
2 - When a transport is selected with paratroopers loaded the only order possible will be to paradrop (cant remember the exact words). When you select the order to paradrop a dropdown of provinces, well, drops down. If, and this is the confusing bit, there are no provinces you can drop into the drop down will contain no provinces. It's not a bug, just poor UI.
Vanilla is superior

As Germany I rebased several paratroopers into my allied Italian African territories.
Of course this soon proved to be a death wish, as my forces had no supplies once they reached N. Africa. My transport planes couldn't even fly them back because they had no oil. I did an air drop supplies mission for a while but my paratroopers ate up the supplies and I couldn't seem to drop any oil there, because my paratroops don't need it I guess... sigh. I lost like 7 paratroops in Africa from lack of supplies
