Dear teachers,
Please look at the following question:
At first everything went well with the project but recently we have had a number of_____with the machinery.
A) disturbances C) outputs
B) setbacks D) distortions

A or B? I am not sure. it seems the answer should be A because setback usually means frustration. But if A is correct, why isn't the preposition following the blank "by" or "from"? Is "with" ok here?
Besides, Dictionary told me that setback can mean "problem" sometimes, so " we have had a number of problems with the machinery" seems correct now.
I am puzzled, help me and tell me why plz, thanks