What am I doing wrong when my timeline scene looks good with the timing, etc, but when I render it into AVI format, it no longer fits together, and the timing is sometimes way off?  Characters aren't moving when they should, speaking is off, people are changing position at different times.  I appreciate your help so much!!  Thank you!

By any chance, are you rendering to an uncompressed 4K AVI and trying to play it back?