"I have recently been getting error messages from the Mach2 while under automated unguided imaging regarding an "encoder error" or as in the case of the attached, "motor stall". While I am not too concerned about getting the errors as none of them seems to affect the quality of my images,"
Larry, are your clutch knobs tight? I found that I could not make them tight enough by hand when I have a bigger optical tube on the mount and need to use an allen wrench to lock them down just a smidge. E.G. if the controller tells the mount to move and it doesn't move as much as the controller says, as measured by encoders, then you'll get this kind of warning. I got these the first night I used the mach2, and since then always tighten the clutches just a little bit more than I can by finder and never see the issue again.
Just a though, may or may not be your issue.
Terri