I've never seen a bug like that. The rig position has never acted up with me and I use it a lot. The rigs are listed in order that they were published, but the order can be swapped around easily in the Project tab of the inspector.
Click the project layer and then click the published tab to see all your published properties in Motion. Grab any parameter and move it up or down until they are how you want it. You can also set their default values here as well. Save and return to FCPX.
If this doesn't work for you, post pics of your published parameter tab in Motion and your inspector in FCPX.
Andy
http://www.timesavertutorials.com