Wocka, Low range is the go. We have a BT50 that burnt out a clutch when backing up a small rise, also things move slower etc.
If you are unhitching when the CT is not on the same plane as the 4by, you will have problems. The reason is that when you wind up the jockey wheel to lift it off the hitch pin, the hitch point moves putting lateral strain on the hitch.
Depending on the angle, you can try rocking the 4by back & forward [gently] or if this does not work, drop the jockey wheel but only wind it to the point where the CT takes the weight off the hitch, then remove the hitch pin on the 4by & drive forward. For both methods I would chock both CT wheels front & back.
PM me if I can better explain this
Regards
Hem