Quick update on the situation. Since changing those extension leads, I've had no problem.... Until today.
I decided to do a non stop 37 km journey (I've been holding off since my good charger blew and my back up charger is slow and under charges to 53v)
And about 5 km away from my destination (maybe a little more), it happened. At first I thought it was just an lvc. I was getting low and seeing my indicator drop down to 45v (un-throttled). Which surprised me because I usually make that journey with at least 46v left at the end.
When it happened, I assumed it was an lvc but when I looked down to the numbers of the indicator, it was floating at around 13v. Usually, when I get an lvc, I see a nice static 42.5-42.7.
I pulled over to check all my connectors. I unplugged and plugged. And I didn't get a spark or any power again. I had to mostly pedal the rest of the way (lucky I was just about there). I did manage to make it work intermittently by unplugging and plugging a few times but every time, 13v after 30 seconds or so.
I can't say that this cropping up again rules out the quality of the wires I replaced as the cause of the issue initially since I've been shutdown free for nearly 2 weeks But considering that it happened after a long 30 km ride and with a drain down to pre-lvc levels, I think voltage sagging might be part of it. I tested my wires for continuity and checked the connectors. They were fine. I'm hoping that after a 3 hour charge, I won't be running into this again.