Ok, this has now been resolved (at least on one printer. Will test on the others once I have rewired them).

To fix the issue, had to update firmware and rewrite the stop.g and cancel.g files. Guessing issue was somewhere in the old firmware or in those configs.

Updated to RRF3.4.4 (Sorry, the printers were in storage for months).
Cleared all entries in stop.g and started over.
Then found it would throw the heater fault on cancel.g but is now fine on stop.g.
Cleared cancel.g, then rewrote it calling stop.g with a couple calls before and it works now too.

On another topic, also found on very rare occasions to be breaking contact on the connector, even with new wires, new molex connector crimped, and new senso with appropriate connector. I have found this can be averted by fixing the connectors so they are not free to move around. ...I need to revise my cable management.