Magnificent ESAM 4000.B Drucktasten

Dear coffee machine members
,we have had a Delonghi Magnifica ESAM 4000.B as a loyal household member for about 15 years. Thanks to this forum, we have in the meantime equipped her with new brew group and new brewing piston. Thanks for the helpful advice!Now

she has developed a new problem: The push buttons to turn on/off and draw coffee - see photo - no longer respond reliably. Sometimes you have to press x times until the machine turns on or for the coffee draw.
These are of course the buttons that you need most often! Has

anyone experience with the repair? We have already opened and looked, but that looks so fitzelig and tricky behind ...
Greetings!

Hi,
sorry - I just realized I posted the question in the wrong thread, but can't delete it.
Sorry!