Definitely not a heat issue. I had the laptop apart to swap the HDD and checked that. Also if it were that, it would've exhibited the same problem even with a fresh Win10 install on the test HDD.
...

This one has been kicking my butt for a while and I just can't seem to sort it out.


Laptop is an HP 15-f039wm, running Win10 Home, with an Intel Celeron N2840 CPU:


Intel Processor N2840 (1M...