Wow, so the mechanics failed but the electrical part still worked. That's pretty shocking, it should have been the other way around every time. I'm trying to think of how the brake system could have been designed that this would even be possible, the only thing that I can imagine is that a dual piston master cylinder had one of the pistons freeze solid so that the whole system failed to move. But that should be pretty much impossible.

One of the disadvantages of regenerative brakes is that if you use them well that you will end up using your hydraulic brakes less than normal which can cause the pistons to seize (and which is an expensive repair if they don't free up by themselves), did the brakes function normally prior to this or did you not use them for a long time?