I haven't got an S, but have observed the eventual drift with every HMD I do have.
I'm under the impression Elite handles its own relative motion tracking, rather than "hard snapping" the position at the headrest directly to your position in real space, in absolute numbers, when you hit the reset orientation key, so any momentary loss of tracking makes the virtual space origin float away from the real world one, rather than realigning as soon as the HMD finds its bearings again.
I'm under the impression Elite handles its own relative motion tracking, rather than "hard snapping" the position at the headrest directly to your position in real space, in absolute numbers, when you hit the reset orientation key, so any momentary loss of tracking makes the virtual space origin float away from the real world one, rather than realigning as soon as the HMD finds its bearings again.