Lens blur filter creates halo in 2021, not in 2019

[pietmtw]

Hello, anybody have an idea what could be causing this problem? Same image, same (admittedly sloppy, but that's not the issue) depth map. Left side is CC2019, right side is CC2021. The lens blur filter in 2021 gives a horrible halo. The lens blur filter in 2019 acts like it's supposed to act, blurring only the black part of the depth map, not the white part. Anybody have an idea how I could get the same behaviour in 2021? It's like it's broken... Thanks!