Help!...Export keeps adding or removing a frame

I'll bet this has been answered before & I just can't find the solution. I have a program for broadcast that is 28min 30 sec long. When I export the project it adds a frame (28:31). If I remove a frame from the timeline it exports as 28:29. It keeps getting rejected from the broadcast inspectors. I thought it had to do with drop frame & non drop frame but nothing seems to help.

The kick in the butt is that FCP shows the program to be 28:30 & so does Quicktime at playback. The Broadcast inspectors see it as one frame too long or short. So does the media info program I used to confirm the length. I hoping someone can easily explain a remedy to get this program on the air cause the deadline is approaching fast!

I really appreciate your help in advance and again I'm sorry if this problem has been addressed before.