@whipsaw - You can call it a hardware problem if you want, but IMO, it was (is) a rational approach to solving the problem of jitter reduction of source-clocked digital data. I'm sorry you experienced problems with your DAC.
With their implementation as I understand it (and I am a digital electronics engineer), there is no "definitive" fix if the source and DAC have significantly different clock frequencies. I suspect this new firmware either increases the amount of RAM allocated to the FIFO, changes the algorithm used to reset the FIFO pointers (e.g. between every song), or both. This won't fix all possible cases, but it will likely reduce the percentage of users that experience the problem from an already small number to near zero.
I don't know why Denafrips chose to wait as long as they did to issue a fix. It could be that other more significant changes were required to the firmware to allocate more RAM for the FIFO, or it could be that they just felt it was affecting so few users that they had other priorities.
At any rate, hopefully this will fix the problem for the users that FIFO overflow/underflow was affecting.
I'm quite happy with the sound from my T+, but I'm looking forward to being able to try out this new update. I've never experienced any skipping/glitching issues, but I have always used my T+ with a USB connection to my streamer (through a Gaia).