I guess that I don't understand why you keep putting RAM combinations in...that evidence problems.
I don't know anything about the test you've run...but I suggest that you download and run Memtest86.com - Memory Diagnostic - http://www.memtest86.com/
If you have 3 RAM modules...I suggest testing them individually (initially) one at a time, letting the memtest series of exercises run for about 1 hour each time. If you get errors...don't use that module again, put it aside.
Then...I would try different pairs together, again 1 hour minimum for each try.
I also suggest that you save the reults of a given try to file on your hard drive.
What I did when I ran Memtest for 4 modules...I marked each module (with a marking pen) A, B, C, or D...ran individual combinations (Memtest will show which module has errors on the results) and then eliminated modules from consideration.
Ultimately I found a pair that produced no errors, at any time.
Your modules may have different timings...and I suppose that memory, like anything else, can deteriorate over time.