Bug: Template rendering error when visiting project's settings

[Seikilos]

With this plugin I can no longer visit /settings page of a project.
I always get a 404 error. Log says:
Parameters: {"id"=>"sandbox"}
Current user: my user (id=3)
Rendered projects/_form.html.erb (8.1ms)
Rendered projects/_edit.html.erb (10.2ms)
Rendered common/_tabs.html.erb (21.4ms)
Rendered projects/settings.html.erb within layouts/base (23.9ms)
Missing template, responding with 404
Rendered common/error.html.erb within layouts/base (0.1ms)

This occurred during migration from 1.4.4 to 2.1.2
Plugin was copied into new redmine and rake redmine:plugins:migrate RAILS_ENV=production
has been invoked.

Even removing plugin and reinstalling master and updating db fails