Hi xer0 and everyone, sorry about my late reply. I was out on a trip ^^"
So yeah, I tried toggling it before/after unplugging and also before/after plugging it back, but no result.
And, thanks to my trip through Europe, I found the problem to be even weirder, because it worked perfectly while plugged to the AC power wherever I was outside Brazil.
Yep, it works just fine when it's plugged to an outlet in Spain, Germany, France or Netherlands. But now, back to Brazil, it's back to acting weird when plugged to AC power.
I wondered if it was due to voltage (since everything in Europe is 220v), so I tried using a voltage transformer, to no effect. The problem persists.
Well, at least I know it's not a driver or other software problem. It's just the power source acting funny. I'll try a couple more things (such as adding a decent ground wire) and come back with results. Don't think many other people are going through the same problem, but I'd like to keep it documented.
Thanks y'all