I am very pleased with my Topping DAC but have found that sometimes, when I play direct from my iPad (through the camera lightning USB adapter) it cuts out after an hour or two. The iPad still seems to see the DAC but no sound. If I unplug, switch the DAC off and on, and plug in again everything is fine for another couple of hours. This doesn’t happen with Airplay, but I prefer the wired connection for replay of hi res (192khz) files. Is there a fix for this?