Transaction in question: 16ac7736552c5791cff5643e6104c76c24018236b2193e014b308efea4f32f81
The P2SH input has a strange redeem script:
This is almost the same as a P2PKH script, except that the hash is checked against the signature, not the public key. It shouldn't be possible to satisfy this script, because the signature message commits to the script, and therefore the signature itself. Without this circular problem, we could have covenants in Bitcoin today by putting the signature (or its hash) into the script.
Indeed, while the hash checks out, I'm not able to verify the signature against the input's signature message. Additionally, the signature itself is strange, it's only 65 bytes and most of its bytes are
20. So how is this transaction valid?