01 transit rear wheel /brake jammed?

2001swb single wheel ,front drive transit .the passenger side rear wheel has jammed .it has happend 3 times in 3 months and it is after a bumpy uphill drive then jamming when doing a 3 piont turn.no hand brake used so it not that. the previous 2 times i have just drove off back down the hill and after a while it frees but this time it feels worse and dont like to load the clucth too much.the last time was in dry condtions so i dont think rust/dirt it to blame. many thanks for any suggestions.

nathan
March 2007