stumbling block
US /ˈstʌm.blɪŋ ˌblɑːk/
UK /ˈstʌm.blɪŋ ˌblɑːk/
1.
a difficulty or obstacle that prevents progress or achievement
:
•
Lack of funding proved to be a major stumbling block for the project.
•
His inability to compromise was a constant stumbling block in negotiations.