See https://forums.factorio.com/viewtopic.php?f=214&t=64842#p398347
In the save file, all UI elements have been deleted. Forcing a UI rebuild solves the issue.
Whenever LTNT deletes a UI element, it also removes the reference to that element. In the save in question the references were still intact. Leads me to believe another mod messed something up (e.g. by calling clear() on the root ui element).
See https://forums.factorio.com/viewtopic.php?f=214&t=64842#p398347 In the save file, all UI elements have been deleted. Forcing a UI rebuild solves the issue. Whenever LTNT deletes a UI element, it also removes the reference to that element. In the save in question the references were still intact. Leads me to believe another mod messed something up (e.g. by calling clear() on the root ui element).