Why don't the glass plates inside microwaves complete an integer number of rotations before the process is complete? Maybe some of them do and I just have a very small sample size of microwaves to check. Maybe it's a case that the user's ability to control cooking time is more important than occasionally awkwardly groping a hot container. But, wouldn't it be nice to microwave a mug and have the handle start and end in the same position?
As an engineer, the solutions are all there; highly controllable stepper motors, sensors indicating position of the plate, calibrated plate turning speeds, and letting the plate complete a full rotate without microwave emission so cooking time is unchanged.
To avoid redesigning the wheel; find the time it takes for the plate to complete one full rotation under load and base all future microwaving times on multiples of that number.
For my microwave, a bowl of porridge with a total weight of 700g takes slightly under twelve seconds to perform a full rotating, with the first rotation taking slight longer. So I plumb in one minute and thirty six seconds instead of one minute and thirty seconds and everything works out. Why not one minute and twenty four seconds I hear you cry? Well, I wouldn't have enough time to cut up and de-stone the regulation five dates. Obviously.