https://www.gruppenrichtlinien.de/artikel/active-directory-security-breach-15-zeichen-kennwortrichtlinie-nicht-moeglich/ (german article - use browser translation features if needed)
Now ain't that cute: Microsoft has done it again. Possibly, they have never tested if their domain password policy even works with more than 14 characters set as minimal password length...because it doesn't.

This would have possibly made it into my top 5 if I had known that at the time of writing 5-crazy-windows-security-problems-that-are-homemade