I second o_e_l_e_o's advice.  Hardware wallets are notorious for having issues with multi-sig.  For holding large sums I prefer cold wallets, which can also be multi-sig.  To reap the full benefit of having multi-sig cold wallets you'll want to only recover them only when absolutely needed, or have them loaded on multiple air-gapped machines that are stored separately.

Another method that may work is to open a watch only version of the wallet, create an unsigned transaction, sign it with the hardware wallet first, then import it into the Electrum wallet to add the second signature and broadcast.  I had a similar issue some time ago, sorry I don't remember the exact details, but signing the transaction with the hardware wallet first was effective.

I hope that helps, and best of luck.