I have done a bit of digging on this one, there is a feature/bug/action where if you cancel/stop/interrupt a g-code file loading it turns the watchdog on.
Could this be the cause?
You are correct
I tested this morning, and if the file-load is called and then cancelled it flips the watchdog thingy to on!
I have no idea why or how that could have crept into the source code but of course its there forever
At least i know that i need to check after each file load now.