No specific source mentioned. The only thing I can imagine is that Mook changed sides a bit later than the rest of Limburg, could be a few weeks. I've read primary sources where troops were camped around the border between Mook and Gelderland, about a brewer whose wife lived in Mook and he himself in Heumen, his brewery in one village, his "mouterij" in the other and he "wethouder" in Heumen. There were spies set on him. about the army in hight alert because of a lot of people moving... in the end it was a catholic procession. etc. etc.