I’ll start off by saying I am not entirely sure where the problem lies. It may well be a combination of events.
I have seen a few instances where SGP issued a slew command through ASCOM TSX driver and the mount did not slew. This has occurred several times at start of sequence, after homing the mount. The home position is very close to my horizon limit and it may be the mount was not tracking when the slew command was issued. SGP thought it had slewed and carried on the sequence. I noted it at the time, slewed to some other position in the sky and restarted the sequence with no issue.
Last night - I was trying the 18.104.22.168 beta and the slew failure occurred between slewing between mosaic targets. SGP was still showing that it was slewing to target and TSX had crashed. I have saved all the various logs and will go through them later to try and nail down when and in what circumstances it occurred. I had been using the sync offset function and I noted this morning that the telescope had not meridian flipped. SGP was still working - once I had Ctrl Alt Del TSX and started it up again, I was able to park the mount, close the roof and start drying it out.
My question right now is that I have not used GNS for a while, so I am ignorant of what it does in the event of a never ending command - would it provide a warning?