[Ofir]

As said before, it’s leaking air.
I can spot some suspects:
* worn out sealing of the air chamber.
* missing sealing material (glue?) around the reeds
* keyboard side clamps

I must say that the keyboard side clamps seem in a great condition. Also, sealing around the reeds seems good and it is hard to spot any issues. Therefore My first guess would be the outside sealing of the air chamber.
I was thinking of getting a sealing rubber stripe, and to put it on the back-cover side so the screws will press it against the air chamber walls. Was there such sealing originally, or was it only relying on the instrument-side sealing against the metal back-cover? Do you have a suggested product for that purpose?

One more thing that I must do, is to replace all the outside screws to Phillips head screws. I simply hate working with old slot head screws! The variety of screws which came with it shows that they were probably replaced over the years. In order not to harm the instrument, do you have a suggestion of how to choose the new screws? The ‘important’ ones (related to the functionality of the instrument) are all screwed into metal holes. I also suspect that some of the screws came with it are simply not tight enough in their holes.