Adjusted alignment not saving

If I add an image, and give it an alignment - it works.

However, if I then edit the content type and change the alignment, it works in the edit page, but on the front end of the site the change isn't displayed.

Very strangely, if I add another image in to the same wysiwyg when editing, the first picture then takes the correct alignment it was given. Then if I delete the second image, the first image reverts back to the very first alignment it was given.

Sorry, I'll try to make that clearer.

I create nodeA, add imageA with left alignment. I save - it left aligns.
I edit nodeA, giving imageA centred alignment. I save - it stays left aligned.
I edit nodeA, adding imageB with right alignment. I save - imageA centre aligns, imageB right aligns.
I edit nodeA, deleting imageB. I save - imageA reverts to left align.

Any insight in to why that happens would be fantastic. Thanks again for the great module.

Thomas