A drifting clock, particularly by that much, is a concern. We expect 60hz mains power and time our controller off that incoming power frequency. We will adjust speed control to handle a range of power frequencies, but as a general matter you should not have power running at a frequency as high as would be necessary to cause that kind of drift (what you're describing would be a fairly consistent 60.09 - 60.12hz, seems like a small difference but for a power company that would be usual).
An insecure thermostat cable connection can result in drift (though usually slow clock, not fast clock).
Otherwise there may be an issue with the controller itself.
Please give us a call, 315-299-3589, to discuss it and try some troubleshooting and/or arrange for warranty repair. It is possible, especially if you're running off grid for a significant time, that you do have an out of spec power frequency or running with "dirty" power which will present a problem for the controller.