>> LB don't allow sending to Electrum
It's not Electrum - LocalBitcoins have no way of identifying which wallet generated a specific address - but rather they do not support segwit addresses. (I had no idea there were
still services out there which do not support segwit addresses. This is ridiculous, and another reason people should avoid LBCs.)
>> HOWEVER after the CB deposit, there is a withdrawal of the same amount appearing in my Electrum history
Either your Electrum is malicious, your computer has malware, or your seed phrase is compromised. (Or, less likely, you have duplicated your wallet via your seed phrase to another device and that has been compromised.)
It's definitely not a fake version. I updated, installed, uninstalled.
Did you every verify the download? If not, it could be malicious. I would suggest that you verify the installer you have downloaded now to see if that is the culprit.
Is your wallet duplicated to anywhere else? How do you store your seed phrase?