I'm having problems with the crop box in Photo Mechanic Version 5.0, build 16765 (2682973). I'm running it on a current Macbook Pro with OS 10.9.5.
There a several erratic behaviors but the one I have had happen the most involves me tilting an unconstrained crop box to level horizon and moving the box along the left edge of the frame. When I do this the crop will disappear and I have to start over again.