Dear MSTDR,
I faced the same issue on yobit . They stole my 18,6 ETHs.
I tried to transfer from My ETH Poloneix wallet to my yobit ETC classic wallet.
it is in the air more than 500 days.
Dominingherzog , does not response, when I write a support message, they reply an automotic messega regarding replay attack topic.
did you find a solution ?
Im not saying that you wont recover those funds but 99% sure that this would be most likely the case.Dont expect for those ETH to be returned yet yobit support doesnt really respond forever.