How about those sticks that showed Memory Errors? Try as many memory testing apps as you can find, but if even one of them shows errors, and you are still not sure, you should take the sticks to your local computer shop that does custom builds and repairs and see if they can test the sticks for you. I have a place near me where I go when I am not sure if a stick is good, they charge 25 bucks but I value their opinion, plus they have testing stuff that I don't have access to.

That kind of service may not be available in all areas, I actually searched for a place for years and finally found these guys.

But if you run 2 different Memory Testing apps and both of them say "Failed" you should pay attention to that, sometimes a confirmed test is all you need.