So I have bitcoin-core wallet.

1. I imported one of the receiving addresses from bitcoin-core to electrum as a watch only wallet.
2. I created a raw transaction using electrum
3. In electrum, I exported the raw transaction as a file (psbt file)
4. Load the PSBT file using bitcoin-core
5. Successfully signed the transaction on bitcoin-core

I repeated the process for the second time and I am getting this error, "could not sign any more inputs"

I searched the error message, it seems be here:
https://github.com/bitcoin/bitcoin/blob/7fcf53f7b4524572d1d0c9a5fdc388e87eb02416/src/qt/psbtoperationsdialog.cpp#L81

PS:
before I did the second try, I changed the passphrase.
bitcoin-core is on an offline computer.
bicoin core v0.21.0

I wonder if changing the passpharse on bitcoincore is related to this problem.
As far as I know the passphrase is only used to encrypt the wallet file? It has nothing to do with the private keys and address like mnemonic seeds?