Adds underground mines, randomly extracting all ores that can be mined without fluid input.
Mods introducing new content into the game.
New Ores and resources as well as machines.
here is the crash log
https://gist.github.com/jarquafelmu/e78216587d5df27c0952db9edab2f664
Which of your mods adds thorium-ore?
Bob's ores
https://mods.factorio.com/mod/bobores
I can't reproduce your error with bobs ores. Please update to 0.5.4, enable debug mode, post the complete factorio-current.log on a site like hastebin.com and link that in your post.
I loaded 0.5.4 as asked and the error didn't happen this time. I will keep debug mode enabled and report back if I catch it.
