Just for completeness, it turned out the sonicTransporter i7 (i7-7700) running Roon Server + HQP Embedded was never the issue.
It was an issue with the Rendu’s at DSD512 with HQP (fine with Roon) - but an update released today via sonicOrbiter OS has fixed the issue at this end.
Tested with a Pro-Ject S2 DAC and iFi DSD Black Labelm, the combination of sonicTransporter i7 + Roon + HQPE + Rendu’s is tremendous value.
Thank you for the first class support @jussi_laako and @agillis . True gentlemen and scholars.
