I'm having an issue wherein if I attempt to "route all", the software routes maybe 25% of the wires in the assembly and then quits - no errors.

I can, however, route any of the components individually (other issues in previous questions notwithstanding).

I can even route by component, then select the entire tree, and start the routing that way, in order to route all components, but this has some issues of its own.

Question is - why might routing quit less than half way through the job?  What might the error be that is causing this issue?