You can see the trimpots and their settings clearly at this site http://www.modezero.com/flanger-hoax.htm
Thanks for your quick reply, I agree – recalibrating this sounds like nightmare to me. I measured the wallwart output voltage in the meantime and it turns out instead of 18vdc it’s actually supplying 25vdc to the hoax. I guess that might be the reason for the distortion.
I wonder if this could have done any internal damage to the unit now?