I've had similar problems recently, ran memtest and my RAM passed some tests, some not. I replaced them with two new sticks, and about 4-5 days later the same errors kept popping up. (Most of the time my screen would just freeze, and also have problems booting up) Normal programs ran fine for me, but any large files or memory intensive programs would crash the computer.

My guess is that my motherboard was the root of the issue, not actually the RAM, which ended up in me having to replace the entire mobo/cpu/ram combo. (With something that isn't over 7 years old, so I don't feel too bad about it)

I hope replacing your RAM fixed all issues, but if your problems continue to persist it is most likely a motherboard issue. (or CPU, but at this point it gets hard to test)