I've had this issue, have you removed the Polaroid back since taking the picture?
In my case I discovered that I accidentally hadn't pushed 2 of the 4 pins in all the way and the back had a gap when I locked it down, I didn't even know it was possible to lock it eve some of the pins were out.
Perhaps you did the same thing? Check to make sure all 4 pins are pressed tightly in the back.
Mamiya: 7 II, RZ67 Pro II / Canon: 1V, AE-1, 5DmkII / Kodak: No 1 Pocket Autographic, No 1A Pocket Autographic | Sent w/ iPhone using Tapatalk