If you have some unshielded CAT 6 or CAT 6a lying around it is worth swapping your ethernet cables out. There is no guarantee this will solve your problem but it will eliminate one variable.
There have been several posts on issues with CAT 7 especially with consumer grade switches and NAS. CAT 7 uses a proprietary connector that is in principle backwards compatible with RJ45 but there is a lot of scope for mismatches between termination and equipment etc. You can read more here:
Hello. Thank you. I thought it could have the relation to the CPU/Memory too, but it is always between 1.2-1.35 Gb / 1.85G available, even during the playout of DSD128 files. I will continue to monitor it, especially when disconnections occur.
It doesn’t look like your NAS meets either the CPU or RAM requirements to run Roon. In this case your best solution would be to use Roon on a properly spec’d Core like your PC. If you are looking for a dedicated Core device, I would highly suggest looking into ROCK: Roon Optimized Core Kit as a server!