Hovering minecart

Minecart left parked on two unpowered power rails. Go AFK. When I return minecart has disappeared (suspect hijacked by a mob). About 60 rails along the track the minecart is located hovering one block high offset from the track. I cannot break or board the minecart. This has occurred 3 times so far over 3/4 real time days. Eventually the minecart does rejoin the rail track about 30 rails 'upstream' from where it was hovering and can be boarded. (I have a screenshot but unable to upload it).