After running Roon from my PC for all of yesterday afternoon and having it dropping out an various intervals during that time, it did eliminate the server’s network card as the cause of the problem. Consulting the Roon logs showed there were still connection failures at each dropout despite there being no obvious network errors otherwise. It turns out my Netgear switch has an intermittent problem on two of its five ports which were causing the comms errors. Replugging Roon directly from the back of my router solved the problem. A new switch is now on order.
As for Roon running on a spinning disc, that’s how it was even on my QNAP for the past nine months as a result of this issue… Roon unstable on SSD [Ticket In] - #10 by Alan_McMillan… that is yet to be solved. Having it on the C: drive of my PC is also no issue: there’s an i7 processor and 32GB of RAM in there so Roon’s response is well nigh instantaneous.