It seems it's not possible to upload the same image twice in one post. Even if you delete it, it will simply not let you add it again.
What browser is this? Have you try that here? it works for me on firefox...
btw, this forum is running Spirit v0.4.x
Yep, same problem here. It's chrome, osx and win.
I can reproduce this on Chrome. Very weird thing. Uploading image A, then image B, then image A again does works, but as you reported uploading image A twice does not.
Found the issue and fixed it --> PR