NVIDIA 3080 failing to decode H.264 level 6.0?

I’m getting artifacts in multiple video players trying to play 3840x2160@60fps video encoded with High@L6 level. I don’t get them if i switch to software decoding.
So, my question is: what it the maximum H.264 decoding level supported by NVIDIA Ampere (3080, for example)? According to vdpauinfo under ubuntu it’s 5.1 for all profiles. I couldn’t find any new information relevant to Ampere myself.

I think these artifacts with high CABAC ref count is just a bug in the driver.