This looks like file corruption caused by failing hardware – could be camera card, card reader, hard drive or RAM.
What you refer to as "the original RAW file" is the jpg preview embedded in the raw file, which is usually not affected by corruption.
There is also a slight possibility that is a GPU problem. You can check this by going to Preferences > Performance, and setting Use graphics processor to Off. If this fixes the issue, you will have to work with the GPU off until an OS update installs an updated graphics driver.