Since my spindle and coolant are controlled by a separate I2C board and the controller doesn't know how to stop them when the emergency stop is hit I have disabled all options in Settings->Events->EStop.
If I hit the Estop though it leaves my coolant and spindle buttons on (as expected), after clearing EStop I can then hit the coolant buttons to stop that, but hitting the spindle button does nothing and it stays highlighted. When the EStop originally hit the Active M-Codes shows a changes from M03 to M05 (I suspect this should not happen in this case). The only way for me to then stop the spindle is the issue a M03 commands followed by a M05 command in the MDI window. Using version 2020.01.17 at present.
Have you given any more thought to being able to store a I2C sequence in the controllers non-volatile memory that it can send out when the EStop is hit? In my case I would want it to send 2 sequences of 2-3 bytes to turn both collant and spindle off.
Thanks
Simon