As a security researcher, I absolutely assure you, the pattern of "checking signatures by checking that the last instruction executed was, in fact, a correct signature check over the right data with the right results" sets off ALL my alarm bells. This is so backwards I don't even know what to say. Just reading through the linked code I'm getting "this might be exploitable" feelings, and not just the aforementioned bug, other parts of it too.
I can't believe others trust these people with their money. They have no idea what they're doing. They're building a ridiculously overcomplicated system layered upon layers of systems where any single mistake can cost them all the funds with no recourse, and aren't even doing it in ways that make sense. It's insane.