@PrTv I am definitely sorry to hear of your continued issues. I am sympathetic to your situation, as I have had more than my fair share of problems with various pieces of audio gear over the years, from various manufacturers.
I have some "bricked" gear that I had to throw away due to no support (LH Labs DAC as an example). I am also currently having some signal locking issues with one of my DAC's (not Denafrips), where the sound stops, and I have to power cycle the DAC or computer every couple of days to fix it (some days I have to power cycle 3 or 4 times a day, it is random). It is very annoying.
I sort of expect issues to happen from time to time. I just try to buy from manufacturers who will provide support and Alvin has always done that for me. It does seem as though you are right that you may need to send in your unit for diagnosis/repair, but it will get sorted out. Hopefully you have some spare gear you can substitute while your unit is being fixed.