I was trying to pocket cut a standard rectangle the other day and again, to my amazement, the router went wild on me and shifted a few times, eventually finding it way into slamming against the left rail completely off the original path. The first two passes were great and I run to grab some items and I come back to this mess. Is there any issue with my rail and/or belts? Tried searching for similar issues but could not find anything definitive. Appreciate the insight.
I would start with the basics, first would be the setscrews for the drive pulleys, belt tension, and also wire connectors. One misstep, and after that it just escalates.
What is your depth of cut? It may be too much and binding causing lost steps.
Did the cutter slip down in the collet, making the cut deeper than it should?