I don't understand what triggered my sawstop.

So the main tool of the shop I work in is a big sawstop table saw. I have made literally tens of thousands of cuts, we use it all day every day. We know the things that set it off, and when to run the machine in bypass. But the other day my coworker was cutting a piece of polycarbonate plastic - something we cut every day! - and the brake went off. His hands were nowhere near the blade, and the material was bone dry, no drop of water there to set it off... So what the heck happened?

I know this isn't "woodworking" as such but I can't imagine any other community with more experience with sawstop. We're sending in the brake cartridge to them and all that, no problem, but for my own sanity I wish I could figure out what triggered it. I don't want this to become a frequent occurrence.