Sentence:  Therefore, even if the author is a celebrity, something may throw a <WSD>monkey wrench</WSD> in an event's success. / It is here where I must mention the <WSD>monkey wrench</WSD> that dramatically hurt events I scheduled during the period of 1996–2001. 
Meaning of the word marked with <WSD> tags:  An unexpected or troublesome problem, obstacle or dilemma.