Sprint Cadence Errors with Rally RS200 / XC200 (Also Vector 3)

This is a long outstanding issue I'm having with both Rally RS/XC 200 and Vector 3 power meter pedals. I'm interested to know if anyone else has encountered the same. 
During hard/fast road sprints the cadence drops to 0 (or extremely low) meaning the power also drops to 0 or reports incorrectly. This is repeatable (see links below). 
Both the Vector 3 and Rally pedals are on the latest firmware and are using a single new CR1/3N battery in each pedal so I've ruled out battery seating issues. 
Apologies for way too many examples... but it does highlight the issue across both sets of power pedals: 
1x Acceleration 16 minutes Rally RS200 cadence drop. 
1x Sprint ~2hrs 9mins Vector 3 drop: 
1x Sprint at 5mins Vector 3 drop
2x Sprints 1hr 10mins and 1hr 12mins Vector 3 drop
Given the repeatability of these and that is occurring across both Rally and Vector meters, I assume the accelerometers are disagreeing with my sprint style?