Environment:
[PC] Brawl match, Etrata, the silencer as commander

Procedure:
1 Cast Etrata, the silencer from the command zone for the first time
2 Attack, deal damage to the opponent and resolve Etrata's ability by shuffling it into the library
3 Cast Mulldrifter and draw 2 cards, one of which is Etrata

Expected:
Etrata is in the hand and costs 2UB

Observed:
Etrata is in the command zone and costs 4UB