Hi Brian,
Your screenshot shows a very interesting behavior, the data seems to be drifting which might indicate a protocol mismatch in the MPU-MCU communication.
The first thing I always recommend is implementing some sort of data-checking logic to validate incoming messages. But in your case, I would make sure that the number of bytes per transfer is the same on both sides.
I can try to help you further if you could provide a stripped down version of the Simulink model that is causing these issues.
– Omar
