throw a wrench in

See throw a wrench in the works.

throw a wrench in (third-person singular simple present throws a wrench in, present participle throwing a wrench in, simple past threw a wrench in, past participle thrown a wrench in)

1. (idiomatic, US) To introduce a problem, dilemma or obstacle in; to complicate.
   • 2020 December 28, Zach Montellaro, “Georgia election admins battle Covid and conspiracies ahead of Senate runoffs”, in Politico‎:

     The pandemic is also weighing on preparations, with election administrations hyperaware that Covid cases could throw a wrench in their plans at the last minute.