Hi @Dellybro,
This sounds similar to: deployProxy regularly errors with Invalid deployment when using Infura - #2 by abcoathup
Can you share the output from your deploy and your hardhat.config.js (Please don’t share any secrets such as mnemonics or api keys)?
I tried deploying and upgrading to BSC Testnet and wasn’t able to reproduce your error.
I used: OpenZeppelin Upgrades: Step by Step Tutorial for Hardhat (though I upgraded locally rather than using a multisig), and https://docs.binance.org/smart-chain/developer/deploy/hardhat.html