[2021] Please help me!

Are you absolutely sure that your loot filter isn’t accidently filtering it out? 500 runs without it dropping is unbelievably close to impossible. That’s like losing 1300 coin flips in a row.

If you are seeing another of the unique boss drops every time then you should probably submit a bug report. Because while possible, it’s insanely unlikely.

Are you always seeing one of the other uniques in the guaranteed drop pool every run?

This is an important distinction that will help understand if this is a bug or not.