If any plugin reports an "internal error", there is a good chance that this is a fault which should never happen. Please report this to support, and give as much detail as you can about what happened:

• Which plugin you are using - you'd be amazed how often this is missed!
• What you were doing at the time
• If possible, a screenshot of the actual error dialog. Lightroom itself can also show similar errors and this lets us tell whether it's the plugin or Lightroom.
• If possible, the plugin's log file, ideally on "debug" or "high" logging. This can be set in Lightroom's Plugin Manager, and the logfile is stored in your Documents folder.