Hi there! This is a known issue with hand gestures. Vision Pro is a little more “aggressive” about reporting joints as not-tracking, where Quest will still give you a “best guess” about where the joints are if they are occluded or not tracking well. As a result, gestures which rely on occluded joints (like your knuckles when giving a “thumbs up”) will fail to be recognized.
We’re working on a fix for this on the Unity side, but in the meantime you may be able to re-construct certain gestures to work with only the joints that AVP is giving you in those circumstances. I’ll ping this thread again when we have more info to share.