Holiday Service Failed to Handle Last Exception

@39x5rw2wtp7mWhile I can't look at your error as you only posted the URL for it, if it is what I suspect it is from the title, it's from removing mods with custom holiday traditions or other holiday mods, and not an error with the game itself. The workaround generally is to cancel any holidays that are scheduled in the calendar (including any ongoing ones), and also doing a "save as" instead of the usual "save".