We've hit this issue (or something related) a few times. Despite IA Support saying that is is triggered by a 'race condition' I don't know if they've ever confirmed that it's a bug (even though I'd consider any race condition to be a bug).
One thing I've found to potentially help is making sure 'persistent' is disabled on any of the properties which have the problematic bindings. It looks like someone else on the forum has a similar suggestion: Flex Repeater instances sometimes initialize null values (embedded view) - #14 by rpavlicek