Fermatas changed tempo of whole piece

Hi people,

I changed to Musescore 2.0 (6e47f74) about a week ago. It's great! However, I've just hit a problem that might have cost me a days work. I was adding expression-based tempos through-out a piano piece. Had finished them all, and then on a final play through thought that the fermata weren't affecting playback. I wasn't sure if they could or not - so checked on the the forum, and found out that you just changed the stretch in the properties tag - great!

So, I selected the fermata - then selected all similar elements then tried to changed the stretch. The interface greyed-out for a while (Ubuntu-thinking-time) and became unresponsive. When it returned, the stretch had been increased to '8' for all the fermata, and playback for the whole piece was very, very slow.

I changed all the fermata back to 2. That didn't change the slow playback.
I changed all the fermata back to 1. That didn't change the slow playback.
I deleted all the fermata. That didn't change the slow playback either.
I changed the initial tempo setting for the piece. That didn't change the slow playback either.

In between all this, I've re-booted a couple of times. Having deleted the offending fermatas, I'm unclear as to why the piece is still playing very slowly. Is there I way I can reset the initial tempo? Editing the fermatas was the last job I was doing after sorting out tempo and layout all day. I really want to avoid going back to my previous verion of the piece.

Thanks in advance for any help.

Peter