I have a Dell R815 with the I bought it used from eBay. It has had a number of problems, but the seller has been good resolving the problems. The problem is, it keeps showing memory errors, so instead of the 256 GB it has, I normally get something over 200 GB, but less than 256. What is odd is the locations displayed keep changing, See the 3 attached photographs.

I've tried reseating the RAM, but it does not seem to help.