some vs certain (2)

Hi everybody,

Could you share with me your opinion about the difference in meaning btw certain and some in these sentences? Are certain and some interchangeable in these cases?

A. There must be some mistake. (1)

= There must be a certain mistake.(2)

=There must be certain mistakes. (3) ?

B. I'll see you again some time. (4)

= I'll see you again certain time. (5)

=I'll see you again a certain time. (6)

=I'll see you again certain times. (7) ?

C.She won a competition in some newspaper or other. (8)

=She won a competition in a certain newspaper or other. (9)

=She won a competition in certain newspapers or other. (10) ?

D.He's in some kind of trouble. (11)

=He's in a certain kind of trouble. (12)

=He's in certain kinds of trouble. (13) ?

Q