DSD is possible but not to the maximum. 256 should work fine
That said I often wondered why roon didn’t properly limit the DSD upsampling to a number that was adequately achievable for the respective nucleus models. This would stop all the issues about trying to achieve the impossible.
This is true for the nucleus, the OP has a nucleus+.
Not what the website says. It says All DSP combinations possible. Since it explicitly qualifies for the nucleus that this is only possible in the PCM domain for the nucleus, one may safely assume that the nucleus+ can do DSP in both PCM and DSD domain.
Again. Not what the website says
Roon promises that it should just work, so any statement along the lines of “your core is not powerful enough” doesn’t hold.
It’s possible it’s a thermal throttling issue I guess so you could return it with this as a fault and maybe they will redo the thermal transfer paste, and retest the system for full rate DSD512 operation.
I spoke to the team about your case, there are a few possibilities as to why the issue is happening. Where are your media files stored, are they on attached storage or network storage? If the network speed is too slow, Roon might be having issues with streaming them.
It’s possible that there is a thermal issue on the Nucleus, as @wizardofoz mentioned and the unit might need more thermal paste added or something similar. Finally, it could be an issue with the Roon database. We activated diagnostics and it looks like you might have RoonBackups being saved to your Nucleus Internal Storage location.
It is bad practice to have Roon scan backup directories that it creates, and may cause some strange behavior. I would move your Roon Backups off the Internal Storage just to check if this is playing any part. Hope this helps!