Last update:
It seems the issue only occurs when I have both memory sticks inserted. If only one stick is slotted in any of the slots the system is stable, but I get way less FPS in games. When both sticks are present, I get decent FPS, but the laptop shuts down in less than 5 minutes from launching the game.
I created a support ticket a month or more ago and still haven’t received a response so I might create a new one.
But both sticks run flawlessly on their own, MemTest86+ passes with flying colors. Even both sticks pass all MemTest86+ tests, but fail in real-world scenarios.
I’m now certain it’s a mainboard issue.