ok my two sense , all my older getzens had stuck bottom and top valve caps and a couple stuck slides , the grease had dried from being put away and not played , which is good considering their age.
my remedy ,hair dryer set on med. heat warm up the slide pull gently, valve caps heat warm up and use vicegrips GENTLY carefully placed over rubber , twist left gently . NOTE: use the slightest amount of pressure when setting the adjustment on the grips ,go slowly, if they slip try to reset , before you tighten the grip, i use the medium size grips .
ok word of caution on the tone balanced the middle bottom cap was very hard to remove , thus i knew i had a problem , but i got it off , what i found was a very hard caked oil and grease in the valves and threads .
But the middle bottom cap does not go on all the way , time to stop and chase the threads at The Horn Doctor .
THIS is not much different than the method John would use to free them , so never watch them work on your horn , if they do have a problem they can fix it , if you have a problem they will fix it , so it comes down to how brave you are ,
and how fat your wallet is .
besides i like to try myself , i am a working craftsman with many years of experience building and repairing things . JUST GO VERY VERY SLOW . Never try this at home unless you are capable of understanding every thing i have tried to explain,, or you can be very sorry!!