When you set the month to January, February, March, or December thermal imaging completely breaks. You either get a black screen or a white screen depending on the thermal imaging type. Night vision works fine. Every other month works fine, except November which does work but for some reason looks different.

The year, time of day, and day of the month doesn't matter only the month itself.

It's easy to test for. Simply start up the editor with just Ruha and CUP Terrains - Core loaded and set the month to Jan/Feb/Mar/Dec. Then play as a unit with access to thermal imaging such as a tank or spawn with a thermal scope. Switch to thermals and you'll immediately notice how you can't see anything.

Here's some screenshots demonstrating the issue: https://imgur.com/a/G7JBkWQ

The issue's been around for a while, however I finally was able to isolate the cause after testing for it.