My friend gifted me his (second 
) FW3A and said that I can have it as it has had a bad button membrane right from the start.
I drew a model in Fusion 360 and 3d printed it in TPE plastic(just a bit more rigid from silicone) and it seems to work fine.
https://www.printables.com/model/351013-lumintop-fw3a-e-button-membrane/files
Let me know if something doesn’t work for you.
