throw a (monkey) wrench in the works
US /θroʊ ə ˈmʌŋ.ki rɛntʃ ɪn ðə wɜrks/
UK /θroʊ ə ˈmʌŋ.ki rɛntʃ ɪn ðə wɜrks/
1.
to cause a problem or difficulty that prevents something from happening or succeeding
:
•
The sudden resignation of the CEO really threw a monkey wrench in the works for our merger plans.
•
We had everything planned, but the bad weather threw a wrench in the works.