I have had very similar issues; it has driven me absolutely around the bend! I am using also using a custom-built AMD Ryzen 2700-X CPU, ASUS PRIME X370-A (AM4) Motherboard, 32gb Corsair Vengeance LPX DDR4 memory, Widows 10 Pro fully updated and UC Firmware V1.10
I initially noticed audio going off in iTunes, the play icon would show a track was playing but no time elapsing and YouTube videos pausing with a message saying restart device, also the mic level input kept going off. My only way to get the audio back and start iTunes and YouTube playing again was to go into Windows sound settings changing devices back and forwards for input and output, also just unplugging the USB to the Studio 26 and reconnecting it.
I have had multiple communications with PreSonus support with no solution, I dare not describe how many things I have tried, sadly PreSonus said they could not help me any no further as my PC was a custom build, which I don’t think is anything unusual, I have to say I was very disappointed with this response. I have been using PC’s for years, but I am not an IT techy! I use the same PC for work, so I did not fancy a fully rebuild with all the printer, multiple bespoke software, passwords, activation keys and God knows what else.
Unfortunately, I am just putting up with it not working, looking to try another hardware manufacturer, thankfully my use of the USB interface is just a hobby, but I must have spent hour and hours trying to resolve the problem.