Hi Wouter,
You may need someone to look at your embouchure. I think the width of the aperture gets slightly larger when more air is pushed through to increase the volume. If you have the correct tension at the aperture corners I think the aperture will reduce slightly when the airflow is reduced. It may need control (rather than adjustment) of the tension. There should be no resetting required.
Do you have a visualiser and can you see what’s happening?
Regards,
Paul.