(© Alex Hughes Cartoons 2010, published under CC BY-NC-ND 2.0 UK, source: https://alexhughescartoons.co.uk/1998/09/spanner-in-the-works/)
Meaning: To be a problem to the extent that something might not work or continue to happen
Polish analogue: Włożyć kij w szprychy.
An example of use: The fact that we didn’t get sufficient funding for the last stage of the project has thrown a real spanner in the works. It’s now doubtful if we’ll be able to complete it.