Thank you both - now I think I understand why my osPID controlled coffee machine occasionally appears to go into meltdown mode.
While this 'meltdown mode' is a useful test of the over-temp thermostat in the coffee machine, it can definitely also result in an unsafe situation arising - especially if the coffee machine operator is my wife who doesn't care how it works, just as long as it works as expected - think scalding hot, steamy-water sputtering out after the operator has failed to check the input temperature is within the expected range...
Now, I can see why bumpless transfers are required for running profiles smoothly, but they clearly do nothing for helping create a nice espresso safely. If you agree with that, I'd be happy to have a go at hacking the firmware so that bumpless transfers are only available when running a profile.
As I'm currently using my osPId Controller for both coffee machine and reflow soldering duties, I think I might qualify as a suitable guinea pig
It would be useful to have a short discussion before I make any (potentially poorly thought out) changes though, so please do share your thoughts and ideas.