trouble with filtering on device

I have two separate mobile themes, one a no-js theme selected as the default mobile theme in mobile_tools theme switching, the other is a fancy one for iphone and android, chosen for those devices using the filters on that page.

switching is by url. Uses mobile tools for device detection, not wurfl because wurfl has an error with the filters. (See wurfl issue queue.)

If you visit http://m.axiom-ins.com or http://www2.axiom-ins.com using an iDevice/android, it may or may not show the correct theme. Seems like theme caching may be deciding which theme is being used, or maybe the filter isn't working as intended. However I have a non-mobile link that uses ?nomobile=true. if you use that and then return to the mobile site via the mobile site link on the desktop page, it correctly uses the iphone theme (sometimes?)

interestingly, the ?nomobile=true remains in the url after I've returned to the mobile site, and if I delete that from the url and refresh, it again displays the wrong (no-js) theme. Also, the full gomobile url for that link is desktopurl/gomobile, not m.url/gomobile. the latter goes back to the wrong theme.