Meta Quest 3 in Ace Rotate 180

I got a bundle which included the Meta Quest 3 512gb v83, w/Ace, Staccato P and a Ace membership for Christmas from my darling wife and have been enjoying it. 
During my last session on the range in ACE I encountered a problem:


While I am standing facing downrange with both hands on the handset, muzzle pointed down and waiting for the start buzzer, my viewpoint suddenly rotates 180 and then I’m facing up-range.  Sometimes the 180 spin happens while shooting a stage.

I don't think I'm touching any buttons, trigger or joy stick; what am I doing wrong to cause this behavior?

Thanks for your help.