MyFitnessPal is working on beta testing new updates to fix major stability issues with its app, but unfortunately has missed the mark on its first beta release. The first beta release, which was set to improve many stability issues, really didn't do a whole lot to fix things, while some even claimed it made things worse. Snowballing from there, MyFitnessPal wasn't very clear to beta testers what was changing or the status of fixes, even making it tough to leave feedback for the app.
According to some tweets from MyFitnessPal to disgruntled beta testers, new beta releases are on their way that should be fixing at least some of the issues. Purportedly current beta testers should have seen messages in the app to indicate it as well, though that doesn't seem to be the case. In the meantime, they're hoping you just hang tight and wait for the updates to roll in — maybe going forward a better feedback mechanism can be put in place as well.
Are you currently using the MyFitnessPal beta and experiencing issues? You can at least know that complaints have been heard and fixes are on the way.