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If the left side is stuck, something is caught in the works, against some protrustion, or a part of the drum is turned up when it should be turned down, etc.
I could advise you more specifically, if you could photograph the drum at the left side, only twice at most - the flash will degrade the drum surface, and indeed, don't expose it to bright light much more than 2 minutes per half hour, or it will need replacing... and post those 2 photos to me.
Try pushing it inward at both sides, also; try pushing it inward first, at the left side only.
Does any of that advice help? let me know - knowing more about the individual case, I can advise you better still, I hope.