So I created my video in 3 sequences then joined them all up on a 4th sequence with some transitions between. The final sequence (clip) I changed the clip speed to 110%. So two of the sequences are 100% speed, last sequence is 110% speed. All is OK on the preview.
When rendered (I did this TWICE to prove it) the sequence that was speeded up was out of sync with the audio by a second or two - I had to reduce the sequence / clip speed back to 100% and render a THIRD time and this was OK as expected (I use multiple sequences like this all the time but this was the first time I had increased the sequence speed of the entire sequence).
Speeded up clips within a sequence have always worked fine - this was an entire sequence placed on another sequence so a bit different to what I have done before.
Note that Preview was fine, only the generated HD 1080p audio was out of sync. Is this a bug or did I do something wrong?