From you what you said, "I'm just guessing", about the "5MP Netcam SC", it had a manufacturing defect where the pcb wasn't grounded to the chassis correctly or had a broken SM cap to ground. When you added a properly terminated STP cable it grounded to the other termination and worked...

I don't know about Ubiquiti Toughcable, but I have never seen STP without a "drain" wire, I believe it's in the standard. I'm looking right now at a piece of scrap of Mono-Price Cat6 STP I'd thrown in the back of my truck. We do use Ubiquity point-2-point for cameras on entrance points. Fantastic products.
The only way that this would help with ESD is if the computer chassis is grounded to earth either through the rack or directly by the ground lug that nobody ever uses... We use it at work when pulling next to high voltage lines or noisy environments. All I'm saying if for general home purposes, I wouldn't use STP. I'm always ready to learn, that's what we're here on these forums.