Given the errors, it's possible that not all of the extensions are being loaded at the correct time. Once the extensions are loaded, then everything is likely fine until the next time the companion starts. There are two potential changes that might be affecting this that we'll need to look into that were introduced in this change.
- Assets are now cached when sent from the server. This seems like a potentially unlikely culprit since once you have the extension files they should be loadable. However, if for some reason the files aren't correctly saved the first time then they wouldn't be available. But since the behavior sounds sporadic this seems less likely.
- The connection mechanism was refactored a bit to support a new legacy mode that will be turned on in 2.64. Are you using legacy mode (i.e., checking the Use Legacy Mode option before connecting)?