Elastic Audio with grouped tracks?

This might be user error, but it's driving me a bit mad....!

Here are 2 tracks grouped together : http://ift.tt/1NSNw4R

I've turned "Poly" on, and selected analysis view : http://ift.tt/1IJo0z4

Then deleted the analysis markers on just the bottom track, and then hard quantised. The top transient is now bang on the grid 10|3, and the second track is still relatively the same distance behind the top one (it seems to look okay anyway): http://ift.tt/1IJo0z7

So far so good. Now look what happens when I commit the elastic:
http://ift.tt/1IJo0z9


What the hell has happened to the bottom track? Why is it so far away from where it appeared when the elastic was 'live'? Does elastic audio just not work properly with grouped tracks, or am I doing something stupid?

Thanks in advance for any input.... :) :)