HELP ...Please help.

exported mp4 (from ppt)

audio is never never exactly as designed in ppt.
the audio is getting more and more later the more slides we use...
at the end of first slide the audio is a say 1 sec later.... at the second slide the audio is about 3 sec late ...so by the time we get to about 8th slide the audio is about 15 secs late ( its as if the transitions are aggregating this delay perhaps ????) ....i have tried all sorts ...
get rid of transitions ( selecting none)
tried allowing for transitions (by adjusting that same amount of pic entry and exit timings)

nothing is solving my probs...its annoying like hell....

the ppt play back is perfect ....but the exported (mp4 ) audio is out ....so late ...progressively late ..more and more ....so by the end of the 5 min video that audio is about 15 secs out ... why ??????
please help ....