I've been noticing an issue with Wandering Traders behaving in a similar manner to Witches where they turn invisible and emit dark greenish grey potion particles.

The Llamas are unaffected by this issue and the leads form a V shape with the pointy end of the V in the spot where the trader should be.

This started appearing in the final Hotfix Update for 1.19 and has since carried over into 1.20