Hi all, thank you for the feedback.
Furthermore, this plugin is closed-source (as far as I know), so it cannot be "fixed".
The plugin is open source, see https://github.com/openstreetmap/josm-plugins/tree/master/public_transport The problem is that maintaining the plugin is a lot of work. I abandoned the development long ago because public transport v2 would have meant too much work, because the scheme has inherent flaws. Any such flaw does fall on the developer multiple times, for implementation, for developing test cases for all the undefined corner cases, for a UI that explains what the software actually does. By contrast, updating to a single different set of tags for stop poles is not a substantial problem.
This would mean you could immediately add all the stops in the click of a button, and sort broken relations in a click of a button.
Since writing this plugin, the relation editor has superseded most of the way sorting features. Thus, it no longer makes sense to duplicate the sorting capabilities in a distinct plugin. I would nowadays add buttons to the relation editor rather than a separate relation editor. There is also an unfinished routing algorithm in the plugin. I never had found a reasonable UI to exhibit that to the end user. Best regards, Roland