Does not work in iMac 5K (Retina, Late 2014)

I had two of these kits ordered to upgrade my new iMacs. After I installed the first kit (test compatibility first) I was in good spirits, the Mac started and everything went well. So equal reingesteckt the second kit and even now, everything went well. So even started with a little image processing. After about 20 minutes, the system is frozen and crashed.
After much debugging I come to the conclusion that the effect modules due to the increased energy consumption (1.5V 1.35V instead of other modules) to crash. Multiple inspections with memtest in single-user mode brought no error of memory to days and also individually the kits running absolutely stable. Unfortunately, but not when all 4 modules are installed.

I will now turn to the recommendations of the memory manufacturer for my model:
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If the link given somewhere, I would have done before that too before ordering ...