I don't know if this has been asked before. Kind of newbie on the whole creating multi signature transactions. I have been using the BlockCypher API on JS for creating multi signature 2-of-2 Testnet Address. I generate the pubkeys and send them to the API request (https://api.blockcypher.com/v1/btc/test3/addrs) and store the body. I can receive coins without problem, the issue is trying to send money.

I tried with the explanation given here: https://www.blockcypher.com/dev/bitcoin/?javascript#multisig-transactions and can fund them. For sending coins the documentation says:

Each party can send their signed data individually to /txs/send and we can correlate the signatures to the public keys; once we have enough signatures we’ll propagate the transaction. Or you can send all needed signatures alongside ordered public keys with a single call to /txs/send.

I tried doing the first thing, since im playing with multiple users on different apps, and this implementation sounds nice in theory, but in practice, I send the first signature to the API and get a good response, but after that, when signing with the other partner, the call gets a bad request code saying that the hash already exists:

"error": "Error validating generated transaction: Transaction with hash 36048a236b9592eb90c433d63d3f527ae59cb8bfeac68a06d96c2e6356a134e5 already exists.

I can verify that the coins are sent. But why? Shouldn't 2 of 2 transactions require both of the owners signatures?? The inputs are even being treated as multisignature

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I'm really confused here, any help is greatly appreciated.

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