`setWatch` interrupt loop for MPU6050 seems to block async processes on Espruino.

Ok, thanks for giving that a go. It's difficult to track down without having an MPU6050 here (it's a contributed module).

If you uncomment the console.log, how quickly is it being called?

It'd be interesting if you could compare getTime before and after the call in dmpLoop, to see if the function call is actually taking the majority of the time or not.

If you're able to change the module yourself, I think the while loop in this line: https://github.com/espruino/EspruinoDocs/blob/master/devices/MPU6050_DMP.js#L121

should be removed, and the check moved into the if statement above.

My hunch is that the interrupt line is maybe getting pulled low for reasons other than the FIFO having data, and that's causing it to enter the getData function and then get stuck polling for more data.