Until recently, we were happily using registration-free COM for our native and .NET COM components. However, we ran into a weird issue where our application started crashing
This issue is related to how SxS calculates the size of the class information. The version number of the assembly is part of this information.
Since it was working with the release candidate version number, perhaps the workaround for you is to make the version number of the release the same length as the RC release.
If this doesn't work for you, there is an established process for requesting redistribution rights for hotfixes. I would engage Microsoft customer support to pursue this route.