Something that's worth noting here:
I've done more than a handful of rebuild-type commissions that usually start out similar to what you have here with what looks like one small issue. What ends up happening with builds that look like this is that, even if I were to fix the problem at hand, I likely would not feel comfortable putting my stamp of approval and having my name associated with the portable if the rest of the wiring inside is shotty and prone to fail somewhere else. Judging by the pictures you sent, I would assume that whoever built this does not have a ton of experience building portables, and might not have things down to a tee where the reliability factor is high. In my experience in receiving repair requests like these, in every case I would end up (with the sender's approval) completely pulling the portable apart and rewiring everything 100% from scratch.
All just food for thought though; who knows, maybe this is a quick fix and that's really all it needs. Just thought my two cents could be relevant here.