Thanks icopress, but it is no longer necessary.

I was in contact with support and we were able to complete the withdrawal successfully, although via TRC-20 and not via SOL or BNB. Whale is taking a closer look at this problem and why the withdrawal is not possible via these two chains.

I have to explicitly praise the support here again. The communication was extremely friendly, he got back to me immediately and actively supported me in solving the problem. That's exactly what you expect as a customer, really great!