When you use the new archaeology brush item on blocks, it creates particles where you're looking and makes a sound. (On a right-handed player,) the particles are swept left at the end of the left-stroke, then the sound starts on the right-stroke. If the brush is meant to be sweeping those particles of dirt away, the sound should be on the left-stroke.

If you switch the hand to the opposite side (under skin settings), the particles reverse direction to still be brushing the wrong way.

How to recreate:

1. Fresh install; default options
2. Create a new world
3. Give yourself a brush
4. Brush something