I'm sorry to hear you're facing these troubles. Would you mind describing this issue more in detail?
Let me mention, though in many cases there shouldn't be any problem reading (& rendering) correctly the previous version of the RC object and object will be identical, in some situations, there will be differences - as several parts have been rewritten. I'm afraid, we can't guarantee its full backward compatibility because of many new features, improvements and bugs fixed and it's difficult to completely discard any possible slight change. Thanks for your comprehension.
Any additional info is welcome.