Hi Bob, Long time. I have seen this happen in the old KCT controller. Full right rotation is the max pot rotation also. In the KCT case, the control bits that were set to initiate rotation sometimes got set in the full right turn setting and were left that way. Can you determine if the rotor was actually sent to 450 or if it turned, uncontrolled, to the right until the end of rotation limit switch (if one is present) was actuated stopping the rotor? If there is no limit switch, then a thermal switch may have repeatedly opened to protect the rotor from burnout.
The rotation bits got set sometimes and were left set when the controller was powered off or the tracking program was closed, etc. when the rotor was moving. This also happened on some PCs anytime the KCT was initially installed and before the calibration was completed. In those cases we had to unsolder the R-L-U-D rotor control leads until the calibration was completed. Your case doesn't resemble this latter problem, however.
73, Roy -- W0SL