Alan,
You may want to doublecheck that you actually uploaded the firmware. If you are in the Gemini Web Server, go to the page where the firmware file is indicated and see if it is the NewGem-Aug-16-2018 file. The last time I flashed the firmware, I noted there were some minor errors of omission in the posted instructions in the File section here, like hitting the Run button after selecting the file to use. (I uploaded them but didn't write them, sorry).
The PHD2 setting about "stop guiding when mount begins slewing" is meant to stop the app from flashing red, and beeping the alarm, as far as I know. Not sure how that would cause a runaway.
Then I assume you mean the Stellarium app has no Stop button. Can't advise there since I don't use it. But if you keep the Gemini app virtual Hand Controller open there should be a Stop button there to use, or keep the physical HC within reach.?
Best Regards,
John
