Have a really old Grohmix that needs its cartridge replaced (picture 1). Grohe support thinks is a 34 434 so they sent me the instructions for that even though the handle is not quite the same. I correctly set it to 100, popped the cap off and removed the center screw but it seems stuck on, the actual knob came off but left the plastic temp ring (and button) stuck on (picture 2) Grohe support isn’t sure how to remove this so I can proceed, and after talking to 3 support folks they actually suggested trying here instead. I did spray some wd40 in hoping to free it, and I can snap the knob back on but still no movement on removing the temperature ring. Not sure if there is some pro trick to this or are there is some other instructions that aren’t 34 434 (perhaps predate 34 434) that I should be following? I did search and read most of the grohmix threads but haven't seen anything this old?