Unforatunately, no, that wasn't it. Mine was already set to No Sounds for Windows. There are several other sound devices in this PC, though, so I'm thinking it may be one of the other devices that was causing this, including various HDMI and DisplayPort ports and monitors, built in sound...which I meant to disable, as I'm not using it, a Plantronics headphone/Microphone.and a Bluetooth speaker So far I've run through the settings for each and set them to the same...48 kHz, 16 bit, by default. I haven't restarted since doing this, but I had turned off my PreSonus mixer, and just turned it back on, and it didn't do any flip-flopping this time.
Tom Kemp