If you do not find it easily on your own then I would call Steinberg support by phone.
According to this SOS article the unit shall have stand alone capabilities.
But see chapter advanced integration that this Cubase/Nuendo feature might conflict with MR Editor.
https://www.soundonsound.com/reviews/st … -mr816-csx
According to the article the device shall be capable to remember its configuration after power cycles.
So maybe you should power down and disconnect firewire connection once the routing works.
Then advanced integration can not change anything on the device.
But I dont know whether you can do everything you need on the front of the unit. "Potentially".
Or .. try to find how to turn off advanced integration as this sounds like a feature that kind of
performs changes in routing automated triggered by your actions in Cubase/Nuendo.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13