A failing keyboard membrane is probably not a common issue with the STBook, but it happened to one that landed at my place for a repair. 

First, I made a pcb option what worked, but it was too difficult to fit and also I like keeping things original as possible. However, when it comes to mass production,  tooling and minimum quantities are huge factors. Luckily, there were few people who showed interest so the project could go ahead.

I scanned and redrawn the membrane same way as the originals look. 

The membrane itself is high quality, made from modern materials. It feels slightly more rigid than the original, but there are no issues with installation.

Membranes are available to purchase. 

The pcb version with micro tactile switches

The finished membrane

Images are subject to copyright.