I'm using Spine 2.2.27 Essential.
My dev guys... I'm not sure, I'll ask and get back to you.
Just to be clear - this problem was happening in their runtime. My role in the project as the animator is just to export the data and send it over to them to implement in their website.
What i mentioned in my previous post about the flipX disappearing when you re-import the data into Spine is my attempt to investigate the problem. From screenshots they've sent to me- the results I get in Spine after I reimport the data (and the flipX keys disappear) look similar.