We have been routing boards for the past 2 days, all of a sudden we started getting an error with the spindle. Shut down, restarted, same problem. Tried to replace the bit and reset head height, and noticed the head would not turn consistently. No visible blockages in the router head. Any ideas?

Sounds like a spindle issue. How long have you been running the current router spindle? If it is more than a year, it may be time to be replaced.

I would suggest that you call technical support to diagnose the problem for sure. They will be able to help you get a replacement spindle.