Thank you both for your answers.
As my skills are so limited I cannot reshellac an impulse jewel. I have now another balance on the ultrasonic right now with its incabloc disassembled too, so I will try this one. Anyway, I've tested this new balance on a 7009 I have for tests and this one also have some problems in some positions, we'll see how it behaves after the clean and oiling of the cap jewel.
New quality brands (Levin or Schaublin are going to be even higher) aren't an option for most enthusiasts, maybe not even for a lot of professionals. No doubt these made in China lathes have a value proposition, however the point is as you acknowledge there are quality issues and the value proposition doesn't change that. Just trying to take a balanced view of things.