I was in a similar situation. Last summer, I helped my dad at his small meat processing plant in New Jersey. The carriage also jammed on a similar German knife. We almost took the entire mechanism apart. In a panic, I started looking for what it was supposed to look like originally. Luckily, I found manualmachine.com , which has a detailed online library of disassembly diagrams specifically for the GS-12M. I found a detailed cross-section diagram of the entire knife assembly, and within half an hour, we figured out where the spring had fallen out and was blocking the movement. Did you remove the blade with a special puller or just by hand, by the way?
M
maniru
@maniru