Bought mine (2021 900 ACE) a little over a week ago. Less than a mile on the clock, so I know they didn't test ride it.
Five miles home from the dealership, no issues. 40 mile round trip test run (uphill, downhill, sweeping curves, 55mph highway), no issues.
Try to commute to work the next day, made it a few miles onto the highway and it threw a VSS Fault while doing ~60mph uphill and dropped into limp mode.
I really did NOT appreciate the sudden drop in RPM resulting in my speed dropping to ~40MPH with traffic behind me. That could have ended quite poorly.
I was able to get it home via back roads.
Codes thrown: C006C & C0063.
Wiring harness has no obvious damage, fuses & relays checked out fine. Tried reseating connectors for steering angle and yaw sensors, and disconnected battery for ~20min without any effect.
The dealership picked it up the next day and I'm waiting to hear back.
My guess would be a bad sensor, but without the maintenance manual, I didn't have much to go on for deeper diagnostics.
It's under warranty anyhow...I just have an irresistible urge to tinker.