I get this on multiple boards, I am using the Pico. I now think this has something to do with interrupts relating to I2S. If I replace my I2S output code with something that just throws the samples away, there is no problem. If I2S were processing many interrupts, could this have all of the effects ...

I am trying to track down an issue in a fairly complex application, but the symptom is very odd. The application is a clock, so one thing it does is display the time. It also plays sounds, which it reads from an SD card and streams to I2S using DMA (but it doesn't use the onboard DACs). It maintains...