"Brake Failure" (luckily still on jack stands)

[1] A stuck wheel cyl will give you a high pedal, not a low spongy pedal.

[2] My guess as to your problem: 10 yr old m/c. They corrode internally. No problem with normal operation, as the seal do not move far with normal brake application. Everything changes when you bleed the brakes. The seals bottom out from the extra travel of the bleeding process, & 'run over' the built up corrosion. Seals get torn & leak, no brakes or poor brakes is the result.