SentrySafe door lever has become very stiff and hard to turn

[ClangClang]

Anyone here ever troubleshoot a safe before?

Recently, in the past 1-2 weeks, the door lever/handle has become very stiff and hard to turn. It is only stiff when rotating it counter-clockwise (e.g. when extending the bolts and locking the door). Rotating the lever clockwise (to retract the bolts and open the door) is still as smooth and effortless as the day I bought it. The safe has been stationary for 2+ years and nothing has changed, including the relative humidity, the contents of the safe (by volume or weight), etc. This issue appears to be spontaneous and recent.

Anyone have any troubleshooting ideas? I'm going to take off the inner door panel and investigate the locking mechanism as soon as I have some free time, but I am admittedly a complete tenderfoot when it comes to locks.