This card has both a long-standing and newly-made bug to its name.
The new bug happened when using Ob Nixlis' casualty cost sacrificing Atraxa, Grand Unifier. Instead of a copy entering with 7 Loyalty, the copy token of Ob simply died immediately. I have had no issue with this prior to the maintenance on 4/12.
The old bug is with Esika's Chariot and Ob Nix. While you should be able to use Esika's Chariot to copy the Ob Nixilis Casualty Copy, which will enter with the loyalty of the creature you originally used to sacrifice, you instead will immediately have the copy die, despite being able to target Ob Nixilis Copy Token with Esika's Chariot (which is normal).
The new bug happened when using Ob Nixlis' casualty cost sacrificing Atraxa, Grand Unifier. Instead of a copy entering with 7 Loyalty, the copy token of Ob simply died immediately. I have had no issue with this prior to the maintenance on 4/12.
The old bug is with Esika's Chariot and Ob Nix. While you should be able to use Esika's Chariot to copy the Ob Nixilis Casualty Copy, which will enter with the loyalty of the creature you originally used to sacrifice, you instead will immediately have the copy die, despite being able to target Ob Nixilis Copy Token with Esika's Chariot (which is normal).