8ga or 4ga is nowhere near sufficent for a battery relocation, because the distance it has to travel, and the ammount of voltage a starter motor requires, anything smaller than 2ga will loose voltage over that distance. Ive got 0ga direct from the battery in my boot to a killswitch, then all the way to the front to a distribution block which then runs 2ga to the starter and the rest of the old wiring connects directly to the other terminal.
I doubt that the display of the distribution is causing the issue, as i have 2 items (killswitch and distro block) with an identical display and never had a problem.
You can use a multimeter to check for current draw at rest, which is what id recommend to do