I listed the ones I know about - basically the UI code is a more fragile than it should be, I’d say especially when the Bridge is involved. There’s a whole lot less hardware with state in the DS than in the DMP where his coding was a much more serious problem.
If the control processor code gets stuck in any loop, hard spin, recurring interrupt, etc. the memory pattern becomes much more regular and hence any generated noise gets more colored and perhaps goes from unnoticeable whitish noise to a low level colored tone. The same can happen if anything affects the configuration of the screen hardware. But these kind of things usually have visible or very audible symptoms which would cause most people to do a hardware reboot. If you are running with the screen off, the FPGA will still make music just fine without the control processor and the first time you notice something wrong would be when the remote doesn’t work anymore. The Jr has the auto input select option so some people use the remote less often than on the DS Sr and it may not be as obvious that something is wrong on the Jr as soon as on the Sr.
It is the case that I’ve had my system on for months and then something gets weird in the sound. But when I think back there are usually signs of a power glitch somewhere else in the house (a blinking clock, etc.) I suspect the majority of the cases where the DS suddenly changes when it was working fine for a while before are caused by power glitches - there’s always a weak spot in any product for power glitches and the in the DS that’s the control processor: basically because there’s much more power supply filtering for the digital and analog boards. The LED for the analog board power supply can last for many seconds after power is lost, but the control processor is watching for power dropping and mutes the analog card so nothing bad happens to the sound as the power bleeds off.