Please dont discuss safes in open forum, it leads down the road to cracking and manipluating very quickly.
You qualify to apply for Advanced access, I recommend you do, then you can talk about safes in the Safe sub forum all you want. =)
That said, it's a Sentry, so I'm not overly concerned, but I will say that those locks are not very good, usually direct drive, and the dial and spindle is usually plastic, so it may just be worn out. You seem hands on enough though, so I bet you can take it apart and figure out where the dragging is coming from.
Thanks for not diving any deeper into safe lock conversation in this sub forum,