My bookshop was recently gifted a GR3750 printer and we can't wait to test it out as it seems to be in excellent condition. However, the drum knuckle in the rear of the machine cavity appears to be 180 degrees counterclockwise from the home position and it is obviously preventing the drum from engaging. I was unable to turn the knuckle even a centimeter by hand so I'm hoping for some advice on options for resetting the drive knuckle using a code or removing the back panel. etc. Thank you in advance!!