My 5 month old Flask works perfectly and always has. I'm not sure what "vape quality" issues you're talking about, but mine remains the best of the bunch.
The earlier runs of DNA40 boards (if you didn't get one with the hosed up display), were a bit better with the TC IMHO. The next to latest, though, with the "refinement" is a pain to constantly have to reset.
All versions, when in Wattage mode, have a delay && a slow ramp up to set power that is more than just slightly annoying to me. Ironically, the DNA30 did not have this slow power rise like the 40 does.
The newest firmware is supposed to disable the refinement, but don't expect VaporShark to help you with that, unless you want to pay them an extra $100. I will have to see if Evolv is willing to help there, but I'm sure they can't do anything about the performance in wattage mode.
Those 2 things do affect vape quality in my eyes. Does it mean I have stopped using DNA boards? No. My hand built Hana with first run board is fine for TC around the house, but I'll never be able to run it in watts mode. My VaporSharks, I deal with the flaky performance as a compromise to give me a compact, stealthy mod.
I just grab for my SX 99% of the time as it's much more enjoyable for me, && I don't have to work around the "quirks" of the DNA40 boxes