the wheels come off

the wheels come off

Things go disastrously wrong; a situation devolves into ruin or chaos. But it's this point in the film where the wheels come off the story, and the whole thing ends up looking like a big, unfunny joke. Where the wheels come off for most people is the failure to set aside any meaningful savings to go towards a pension or a mortgage.
See also: come, off, wheel
Farlex Dictionary of Idioms.

the wheels come off

things go disastrously wrong (causing an enterprise to fail).
2006 Sunday Times There is not much a captain can do when the wheels come off and batsmen and bowlers underperform.
See also: come, off, wheel
Farlex Partner Idioms Dictionary
See also:
  • be going to hell
  • bushel
  • one rotten apple spoils the (whole) barrel
  • one rotten apple spoils the (whole) bunch
  • one rotten apple spoils the (whole) bushel
  • rotten apple spoils the barrel
  • a bad apple spoils the (whole) barrel
  • a rotten apple spoils the (whole) barrel
  • a rotten apple spoils the (whole) bunch
  • a rotten apple spoils the (whole) bushel