Do you have the same dropouts when outdoors? If not, it could be that you have a really noisy environment (wifi, bluetooth, microwave oven, etc…)
Try putting either Garmin or both of them down under the bottom bracket and seeing if they continue to have dropouts. If you run TR via ANT+, do you see dropouts from the Quarq and/or Kickr?
so I put my watch under the bottom bracket and it was perfect! i think you are spot on with the noisy environment. the edge 520 does drop out outside, i will often look down and see a zero power reading on it, i can’t keep as close an eye on the watch, but assume its better.
That’s both good and bad news. Good in the sense, there were no dropouts. Bad because you have to get it so close to the Quarq. I would still contact Quarq. Indoors or outdoors, the Quarq signal should be stronger than what you are describing.
I had the same issues with the Vector 2s pedals I was using, so think its the edge 520, rather than the Quark.
I have both a 935 and 520. Many of my riding buddies do as well. The ones who have had issues w/dropouts were all the result of their power meters. Most of them were gen1 or gen2 stages. A few were the new Vectors which I think had a battery compartment issue.
It could be you have two bad Garmins 
If you put the 520 closer to the Quarq, all good?