We have the same problem here and it is not the white space, because all our previous products do have white spaces in pictures and all worked well. The problem appeared 2 days ago after the latest VM update.
Here is a link to the product and you can try sharing it on FB - no content at all , only the page address:
www.handcrafts.bg/bg/%D0%BF%D0%BE%D1%80%...-marieta-detail.html
If you try another product - no problem even with white spaces in image names!
All other buttons work fine. Only the Facebook share is problematic!
Please help!
EDIT: Suddenly everything started to work fine ... we did not touch anything and it fixed by itself! Strange.