Fist of all the height adjustment is build into the collar so do not
wear it again ;)
In general the height adjustment does cause this and it moves you
lower never higher (because for most or many poses have them hovering
over the ground).
Best go to the OC HQ at fetish network, and grab on the upper floor
the "Height adjustment" tool from the R&D vendor which does also have
a notecard where it explains to "turn height adjustments off"