I didn't know it was a problem until this game jam lol. The way I rendered shadows was to draw a black rectangle over each strip of wall with the opacity changed depending on the distance. But the opacity is a string. Because of this, any computer set to European regions, and I imagine others, expects something like 0,5 instead of 0.5 so it doesn't know how to render it.
I found a way to force the number to change based on regional settings in the post-game jam bug fixes. Good to hear that the post jam update works.