Print module and missing breadcrumbs of Crumbs modules
It seems the router path for print/.. pages is always "print". See the print_menu() hook implementation in print.module.

You could write new Crumbs plugins for these paths (one for parent-finding, another for title-finding), with a logic somehow like this:


The parent path for "print/a/b/c" is "print/" + the parent path of "a/b/c".
The breadcrumb link title of "print/a/b/c" is the same as for "a/b/c".


The plugin could live in a custom module, or in the print module, or in the Crumbs module (patch welcome).

(This still needs some tinkering and experimentation. I'm afraid if I put it all into this answer, then I can as well just write the plugin myself and add it to the module - sorry..)