The new Flex 4K tuner, it still glitches out signal wise same as the Connect Q did before it died...so at least i know it was not the tuner hardware.
I had a problem with my receptacle where the power plugs in and SD replaced it right away under warranty.
Got replacement Connect Quatro...It came in a Scribe box that was markered out and had stickers on it to say Connect Quatro.
It is quite beat up, scratched etc. For sure well used 
The new, direct from the HDHR store site, Flex 4K came in a plain unmarked white box and i did get that a week sooner.
The i guess "refurbished" Connect i got, i only powered it up and verified I can access its GUI config, then put i back in its box and tossed it in my closet for backup.
I do NOT like getting such poor condition/re-furbished devices back when i have to do an RMA for a mint condition bought brand new device.
Kinda surprised, since they sent me a brand new Prime back when i had one that failed and did RMA for that.
That's disappointing the new Flex didn't solve your problems. I just emailed Silicondust asking if the ATSC 1.0 tuners in the Flex were the same as the Quatro. I have two Quatros and they both work "poorly". I've tried attenuating the strong signals, filtering through an Avant-X, changing cables, etc. yet some tuners on both of them flake out on certain channels after a few minutes. They are NOT overheating - it's about 71 in here at the moment.
I suppose I can get a Flex on Amazon and return it if it, too, is junque.
EDIT: I heard back from a non-techie at Silicondust. They said the LAST batch of Connects used Sony tuners, while earlier versions used MaxLinear. The Flex uses Sony tuners.
I suspect it's more the overall design of the device that matters most.