Ethereum Dropped & Replaced

I once more encounter a problem with Ethereum. We have sometimes certain amount of collateral on 1 address and then send out 5 to 6 payments that should go as fast as possible out (clients don't like to wait for refund).
Now our software works great, but when 1 user tries to refund to multiple adresses, we face often than only 1 of the transactions gets thru, while the others get "Dropped & Replaced".

as far as we know, this happens due to the fact that the last transaction gets confirmed first and then all others are replaced by this transaction. The problem is, that the TX gets officially the status "Success" which then by our system is detected as "work done".

we already placed a 10 second delay into the sending mechanism and we always use the same amount of gas for all transactions, but somehow, that seems to have improved it but by far not eliminated it.

does anyone have an idea, how to avoid and if not possible, track the transaction as dropped so we can reissue one?

the option of spreading the funds to multiple adresses is not viable