Short: Rätsel vs. Rätzel
While working on a German article I came across the word "Naturrätsel" and when looking up the meaning I usually just read the word, hear it in my head and then type it out without looking at the original text. It's a small way to do ear training and spelling practice with German. After not finding the full word on LEO , I tried the main part of the word Rätsel. (Some German words are combined together, and the main word is at the end.)