upset the apple cart
US /ʌpˈsɛt ði ˈæpl kɑrt/
UK /ʌpˈsɛt ði ˈæpl kɑrt/
1.
to spoil a plan or arrangement
:
•
He didn't want to upset the apple cart by bringing up his concerns during the meeting.
•
Her sudden resignation really upset the apple cart for the whole department.