merge mining tag encoding is incorrect
https://github.com/monero-rs/monero-rs/blob/544a0a79332d5007663fea2d5c6ba6085852760b/src/blockdata/transaction.rs#L936C64-L936C64

It is hardcoded as 33 (32 hash + 1 x 0)
It should be 32+length of the encoded field