Well, shit. Makes a lot of sense.

I think I have personally avoided a lot of trouble because I manually adjust the voltage/timings of my memory. When I add a second kit (with what I thought was the same, clearly not) I would loosen timings and settle on a middle ground. Not actually knowing there was a small difference between the two 'identical' kits which could cause me issues. I appreciate the read.

*edit*
I won't be buying now and then later, i'll be getting it all in one go from now on.