Problem getting nesting to update

I am having a problem with a nested sequence updating.
If I need to make changes to the original video or audio, I double click on the nested sequence which opens up the original sequence. I then make my changes either cutting out or adding to the sequence. I then close the sequence, but here is my problem. I sometimes see the video has updated but the audio is not updated and is therefore out of sync!
Is there a trick to updating it or am I doing something wrong?

Another question is how many nests with in a nest can one have, Is there a safe limit?

Thanks.
Andries