No. Unlinked memory has worked fine for me so far at various combinations. There are still some holes, but it works out quite nicely.

I'm still not through with this strange issue of instability I encountered. One day the board runs 18h+ Prime, the next day it'll freeze after 3-4 minutes. Without any changes! No temp issues (none that I can measure anywhere), no voltage issues (I don't see any fluctuations, psu can do much more than it has to do right now). I really don't get it.