Test maneuver profiles?
I used to do diagnostic testing on UH-60s in the Army. We'd do ground runs and test flights in various profiles. Sometimes I'd even add weights to vibration absorbers in flight.
The sensors, pickups, and accelerometers in the AVA (Aviation Vibration Analysis) kit told us all kinds of crap based on the maneuver or profile being performed. To ATC, it often looked like the pilots has lost their minds.
Probably something of a similar nature going on here.