funkydiscoduckI know this is a late reply, but I managed to fix the issue by changing to a totally different switch. Looks like the Halo switches are largely defective. I bought a stack of KBDFANS t1's, installed them, and the problem is completely gone.
PigmonkeYI assumed this was the case, I had the halo trues. My board is on its way back to MD for a refund.
I planned on getting a replacement, but I had to pick up the k70 mk.2 SE as a stop-gap to "get by", it's the version with the cherry mx speed switches and pbt caps, turns out actually liked it quite a bit so I went with a refund rather than a replacement. With CTRL, I had issues with the stabs on day one (they are the lowest quality trash, even compared to this mass produced corsair) and some of my LED's didn't work.
The project was on sourceforge but I can't find it. This link has re-hosted the file. I would only consider this temporary, and would plan on swapping out your switches or the whole thing (depending on your preference) at some point if you don't want to rely on software forever.
https://graphicscardhub.com/how-to-fix-keyboard-chatter/