I was doing a hunt and got a modifier for a legendary weapon to drop with some affix.

When the hunted monster died i did not get the Legendary weapon drop.

This occured multiple times with different legendary drop modifiers in Act 2 and Act 3.

Some others are having this issue as well (see link)
https://www.reddit.com/r/Wolcen/comments/k9iw8i/prey_will_drop_a_legendary_accessory_didnt_drop/