The pattern looks like a GPU, more specifically a problem with VRAM.

This looks like a low to mid range HP laptop, so I question whether or not it even has dedicated graphics.

Systems with integrated graphics share RAM to use for graphics functions.

To test VRAM, one would use Nvidia MATS/MODS or AMD TServer/Memtune. They are not very accessible for the average user.

To test RAM, use Memtest86. This one is free and relatively straightforward.