amendolajamie wrote: Thanks for that link. That does seem to be the same issue. I have also discovered something tonight. From the logs of successful vs unsuccessful slew a difference that I noticed is that the failed slew has guide pulses happening after the slew is issued. I use PHD, and have checked the "don't guide while slewing" box, but somehow guide commands are still getting through. I tested the idea that the guide pulses are triggering this bad behavior, and was able to confirm it. I did almost a dozen slews around the sky with no problems. I then started guiding, and did a single slew, and it went haywire. It seems that the mount/gemini is supposed to handle this gracefully, but it does not. It also seems that phd2 is not supposed to be sending guide pulses if a slew was started.