Pneumatic flush valve failing

[Plumbjam]

Hi all, I've got a problem with a Gerberit pneumatic dual flush valve.
It has two buttons on the actuator plate, when pressed individually they do nothing, you now need to press them both at the same time in order to get it to flush. The toilet was installed around 5 years ago with no problems until now.

Any idea what this could be and how to fix?

 

[Riley]

Do you know the model? Is it a bellows type set up? If you can remove the faceplate can you blow down the pipes individually and achieve a flush

 

[Harvest Fields]

We need pictures for this one mate. Could be the tubes or the syphon itself. In my opinion, it isn’t the flush plate that often.

 

[rpm]

IF hose`s are not a tight fit to the spigots behind the buttons then I have cut 5mm off the hose`s before and it worked or you can replace the bellows.

 

[Plumbjam]

Cheers for your replies, I'm gonna replace the bellows