I always had to, independently if DSM6 or 7, restart Roon (in RoonOnNAS) once a week as some of these thugs stole memory over time. Amounting 60% coming with increasing performance issues. Stopping the Roon package exactly fixed that every time on my 16GB DS1517+.
I’ve got memory stats going back more than a year on my NUC (Debian core). It used to leak badly. Will have to check. While I know the pic conveys good news, it does look as though your core has has a cardiac incident