I’ve found on a similar note (sorry if this is hijacking the thread), that having multiple versions of a plugin installed can cause issues too.
It creates a new folder for each version of the plugin in “%appdata%\McNeel\Rhinoceros\6.0\Plug-ins<plugin>”. I’d assume that only one of these is intended to be loaded, but somehow I (and users) often get initialization errors when there are superseded versions there. This is even with the dependencies ILMerged into a single .rhp, so it doesn’t seem likely that there’d be a dependency mixup. Removing the older versions causes the plugin to load correctly.
I haven’t yet been able to extract enough debugging information to figure out why this is, so any advice would be welcome.