I see Unknown Npc System listed there, my guess is that somehow the json text of that particular weapon was corrupted. Should be fairly obvious once you look at the JSON file itself.
Did you delete the old NPC and lcp data from previous installs of the LCP in owlbear before installing the new one? (it could be the case that they do not cleanly overwrite each other.)
A few things to try:
Try updating the lcp file in Comp Con, and then deleting the old NPC, before regenerating your JSON for use in owlbear.
Try making sure that the lcp file in Comp Con and Owlbear are the same version. (Delete the one in OwlBear first, and then import the newer lcp file [warning: I can't speak to whether this will automatically delete your old NPCs or if that may break them] )
Try deleting the old NPC in Compcon . In some cases Compcon will simply save old configurations instead of checking their systems against its lcp counterpart if the NPC already exists (hence why you can rename things). Once you recreate the NPC, export a new JSON, delete the old NPC from Owlbear and import using the newly minted JSON.
I recognize this is a lot of trouble to go to just to fix one NPC. Personally I'm of the camp of living with the silliness and running off Compcon (that is my preferred way to run).