When I was fault finding my RAM (turned out to be something else) I used memtest86. Tested each stick individually, removing the rest and booting with just one at a time. I ran mine with XMP on then off. When done I scrambled the locations of the RAM sticks, so none were in the same position, and fired it up for use.
MemTest boots from a USB and if there is a RAM flaw it will find it. In my case, the XMP freq (3600) I was trying to run at was not supported by the Mobo, even though it explicitly said it did in the QVL. That was on an ASUS. Lowered the freq (3200) and all was well.
Check your Mobo manual to find which slot to put the single stick in. Cheers.