Then the real question is how did you set up the Linux wallet in the first place? It would appear that it is a MultiSig, as it is only "partially" signing the transaction. The question is, what Master Public Key did you use as the co-signer?
I had made a previous successful transfer of BTC from Linux to Mac to check it was all working. It was, there came up in the Mac wallet automatically the transaction to counter sign. I had not even been made aware then of the use of loading a saved transaction as I hadn't needed it.
Your previous transfer of BTC from Linux to Mac... did you just send to the address that the Mac was displaying under "receive" and the BTC came up in the Mac wallet? Or did you actually create a partially signed transaction and then transfer that to the Mac and then sign and broadcast from the Mac?