Freiburg 12 Studio: blowsssssssssssssssssfssssffffsfffsfffff

Thanks to your suggestions the first rock has been brilliantly passed: now Ein / Aus works perfectly and also the bulb indicating the Ein works.
Today in Hungary it rains, the air is cooler then .......... man at work .
The second rock I hope to solve thanks to your help: there is persistent and continuous breath, but that does not change with increasing volume.
In a volume position it disappears but if you move the potentiometer even of a fraction of db, this resumes.
The most obvious thing, spraying with the contact deoxidant, did not bring anything good.
Any suggestions?
Thanks in advance.