@sketch11 The problem is definitely in the command sequence. There is an extra prompt that is not being accounted for. As I said - All you have to do is open one of the troubled files MANUALLY, and perform the "-DGNIMPORT" command MANUALLY to determine what prompting in the command is different!
It is certain from the feed you just sent that the prompt that is not being accounted for is "Specify mapping setup or [?] <Standard>:".
If you can determine why it is asking this on some files and not on others, you have the answer and we can figure out a contingency for it.