Signing a Segwit Multisig Transaction

I am creating some test code which can create transactions and sign then, I already could do it with NON-Segwit multisig address, they were signed using my code and broadcasted. But when I tried with Segwit multisig, I got problems, it was not signing it right. Can someone walk me through the steps of creating and signing a multisig segwit transaction?

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