You might have a local transaction in your wallet that this transaction builds on top.
You need to either broadcast or remove the local tx."
I'm really concerned? because as far as I'm aware my BTC is still confirmed on my main multi-sig wallet . On the wallet that I recently restored via your advice(laptop). I'm currently shown the original BTC transaction, but with a local transaction that is adding almost the same amount of BTC to that wallet but the inputs for the address are unknown, which shouldn't be possible?!
Since the network isn't aware of it, it will cause that "bad-txns-inputs-missingorspent" for spending a missing input.
Don't know how you got an inbound local transaction but it's mostly caused by having an unconfirmed transaction dropped from the selected server's mempool
or for outbound txns; created a transaction but didn't broadcasted it and used "Add to History" instead.
"Address Unknown" are just scripts that Electrum can't decode, you can try to tick "download missing data" in the setting icon on the top-right side of it to see if it'll update.
If not, it's impossible to tell without the actual raw transaction.
In any case, backup it first by opening the transaction (double-click) and using "Share->Save to file" menu; (in case you need to restore it)
so that you can safely remove it from your history via "Right-click->Remove" so it wont be used in your transaction.
Alternatively, you can enable the coins tab via "Show->Coins", then go to that tab and freeze that specific output through "Right-click->Freeze->freeze Coin".
Removing the local transactions has fixed the problem and now I've transferred all of my BTC out of my electrum wallet.