Sorry, I do not have the bandwidth to dig into that. I imagine it could be either:
- An issue with the way Mapshot removes its own event handler.
- Some behavior about multiplayer & mods (e.g., adding a mod later). I'm really not familiar with the details of Factorio multiplayer.
For the event handler thing, that would be around here. From the error message, it seems that remove an event handler might be an issue for multiplayer. The idea here is that Mapshot registers an event handler to trigger itself on startup when requested from the command line. As it is a one-time thing, it unregister itself to avoid having an extra per-tick useless handler. If you have the possibility to customize the mod, trying to remove the line where it unregister might help.
