I'll chime in here as well. I have had this same issue using my ASIAIR Pro and Ioptron CEM25EC mount for years now. I have tried every solution mentioned. New cables, dedicated separate power supply for my mount, lose connections etc. Nothing solves the problem. I even have tried using my backup OS that I made the first day I got my ASIAIR Pro. At this point I am just living with the problem. Some nights I'll get out of bed and restart my Plan rather than lose the rest of the night.
I use PLAN mode almost exclusively because clear nights here in New England are so rare. I like to take full advantage of them. Typically I'll program in 3 different targets for the night. All sequenced to image as they move through my FOV one after another. Only very rarely will the Plan run as it should and all three targets be imaged.
Most nights I get one of two error messages. "Stop tracking failed", or "Mount disconnected". Also these failure notices always happen at the completion of imaging one target, at the time the mount would then slew to the next. At that point the Plan fails and eventually the ASIAIR shuts down the scope left pointing where it took it's last image.
I am now certain this is some software issue within the OS system since without physically touching anything all I do to reconnect the mount is to cycle the ASIAIR back on, and the mount will then reconnected and I can then send to home position.
The fact that there seems to me many of us all with different mounts suffering from this very frustrating issue certainly also suggests to me a software issue.
I do believe it's well past time for ZWO to look seriously into this very frustrating problem.
