As soon as 180704-2 was downloaded and installed at 8:31 pm (UK time) the issue reared it's head again. HTTPS sites all became unreachable. I was in the middle of watching a YouTube video when the stream was interrupted, refreshed and got the 'SSL_ERROR_RX_RECORD_TOO_LONG' error in Firefox. Tried in Chrome and got a similar error on all the secure sites I tried to access. Unchecking HTTPS scanning made all the secure sites accessible again. But, at 8:52pm another definitions update occured, still 180704-2, and the HTTPS issue is once again fixed.