We have released patches for version 3 and 4 of the Mendix Business Modeler this week. These versions contain fixes for issues reported by our partners. You can find both installers and the release notes on the App Store: 4.4.3 and 3.3.6.
Unfortunately, we have now found that in certain forms and during navigation other problems can arise because of subtle timing issues. Those problems occur in all browsers, not just Firefox, and they are hard to reproduce.