When I play D sharp just above middle C, this then causes the key of E to activate also.
The key of E can be restored to the non-playing position by some force downwards when D sharp hammer remains in the striking position.If get all keys in playing position, then I can playC,D,E and F with no reaction from D sharp.
I have tried numerous cures from the internet involving foreign objects, bent pins,tight pins due to felt problems, ensuring correct alignment of oval head front pins , keyboard interference from front rail and squirting silicon spray in numerous possible sources of trouble but to no avail.
I should add that I am attempting to get the instrument playing again under my own steam really as a project for my dotage. The innards of the instrument are fascinating and were a complete mystery to me despite years of playing.