If you've already talked to a slaver group as an outside road event, when you cancel the slave buy list in umbra the menu appears for the road event with the fight slavers option etc. You can press cancel again and it returns to the umbra menu. This is a pretty obscure bug and looks harmless however you can repeatedly choose to fight the slavers and get another previous battle instead so it might be exploitable (with the right battle).
I'm guessing the cause is this check on guildlocation and location which is in the wrong order (or using different variables).
outside.gd
func _on_slavelistcancel_pressed():
if guildlocation == 'outside':
get_parent().get_node("explorationnode").call(closefunction[0], closefunction[1])
get_node("playergrouppanel/VBoxContainer").visible = true
elif location != 'umbra':
slaveguild(location)
else: