Question Laptop won't turn on with a specific screw on the back cover tightened. Possible short?

Aug 2, 2019
Greetings. I'm having a rather strange problem.
Couple weeks back I spilled some tea on the numpad of my old Acer Aspire V3-771G. The keyboard was toast, so I swapped it out for a replacement.
When I was done swapping the keyboard the laptop wouldn't turn on. Symptoms: the power light would come on, but there would be no fan sound or CD drive startup sound, a couple of seconds later the power light would turn off.
After a few attempts I somehow found out that it would turn on with the back cover off. Weird. Eventually I tracked the issue down to a single screw that wouldn't let the laptop start. Alright, I just won't tighten it, no big deal. Unfortunately, the laptop occasionally turns off if I tap it with some force around the spacebar area (the screw is around that area as well) and I'm having some difficulties reproducing this behavior.
I disassembled it again today and found some barely visible residue under the ribbon that connects the keyboard to the main board, must be some liquid sipped down the ribbon. Cleaned it off with acetone, but still no luck.
The only wires that run through that area are the keyboard ribbon and the speakers wire, neither of which seem to have any compromised insulation.
So what could it be? A short of some kind? If so, is there a way to diagnose it without a multimeter?