If your swipe gestures home bar thing is stuck and won't respond to your swiping, there's a way to temporarily fix it without restarting.
When it gets stuck, open your notifications, open Settings, and rotate the screen (stuck in portrait mode, turn phone landscape mode). Make sure rotation is not disabled, too. Then, use the swipe gestures to go home, and when you rotate it back it should work again.
This doesn't permanently fix it but hopefully the next beta is coming soon, now that Android 12 is officially released to AOSP.