I'm having the exact same issues with the Rift S as well, only on ED which is a real bummer. I have to reset HMD almost 10 times a minute, making the game almost completely unplayable :/ Try to only dock into a coriolis station while your seat suddenly jumps below the dashboard and feel the pain :'(
I have bound the HMD reset function to a button on my HOTAS (X52, D button), this works but when you're in the middle of a fight and your seat position won't stop moving back to a weird spot (below the dashboard) and you are constantly hitting your assigned button to reset the HMD view all the time, it's not just annoying, it's a real pain!
If ever ED devs would like to have a look at it I will gladly send them anything thay might need to help them solve the issue, screenshots, videos, logs etc... and I'm at their entire disposal (so guys don't be afraid to ask). So far I haven't been able to solve that issue by myself, have checked everything beyond imagination to try to narrow down the issue, USB power, updates, video drivers etc etc... no luck so far. All the rest of the games work perfectly well and even when I have to hit the occulus button on the right controller to get to the desktop to reset the view, and then back to the game, that position stays on without any problem. This situation only occurs on ED (not to say MY favorite by far, of course)
For now I'm quite forced to continue playing the old fashion way... mouse and monitor and leave VR Elite aside.. until the issue gets fixed hopefully :/
Oh and btw this is my first post on the forum (althought I've been an elite fan since.. 1984 and have over 900 hours on ED) so this is a big "hello commanders"