I get the same thing occasionally, don't know why, but here are some things I do to get around it - maybe worth a try.
1. delete the problem bar, then copy and paste from another section if possible.
2. make sure no hidden automation is applying to the problem bar.
3. make sure there's no "overhang" from previous bar overlaying start of problem bar -eg use the off grid red mode to peel back any sound from the previous bar to make sure the problem bar has a fraction of silence before it is due to start. hope this makes sense?
Finally, if all else fails, I have even had to run a parallel track underneath just for the length of the problem area, then mute the problem itself (even though it doesn't play) and as long as your settings are identical for the parallel track..voila, your exported wav plays OK.
Hope this helps