Probably the problem was with GFX100 firmware (at least in the first case). It was fixed later by Fuji and maybe they provided workaround for LR and C1. See PL7 Shadow Banding - DxO PhotoLab - DxO Forums for some analysis by @noname and GFX 100 PDAF banding is fixed - the last word (kasson.com) for some background.
EDIT: Oops, it seems that in this case GFX100 PDAF banding was a different issue. Nevertheless, I had no such problems with several Nikons (D4/D780/Z8) in PL7 and the analysis by @noname has shown that the problem was with GFX100 RAWs.
Note also that some Premium LUTs recently provided by PL7 may cause posterization in certain cases, but the reason is in LUTs themselves, being ‘locally discontinuous’.