As with most things, the default position is that longstanding science is right and Einstein is right.
If that leads to the unexpected (to a layman) result that chemical reactions convert mass to energy, then it's time to hit the books to find out how and why.
It's interesting how many people will try to stick with common sense when it conflicts with reality.
What's even more interesting, perhaps, is that Einstein himself had serious concerns about quantum theory.
My guess is that Einstein was completely convinced that quantum theory always generates the correct answers. But the nature of quantum theory is that only the probability of a given outcome can be calculated. The actual outcome varies randomly as described by the mathematical probabilities. I believe that Einstein died a proponent of the "hidden variables" idea. That is, Einstein thought that "God does not play dice". Einstein thought that there could be hidden variables which dictated which of the possible outcomes of a quantum-physical experiment would occur.
Since then, there are some convincing experiments which indicate that quantum-physical events are truly random and such outcomes cannot be completely predicted.