I think it's a good idea to stop this train before it derails completely (although I'm not sure it hasn't already)...
So, to sum up: The issue that user has is that they were relying on bugged behaviour (GMS 2.3 update changed the way image_index was calculated) without realising it was a bug, and when the bug was fixed (image_index is now dealt with the same way it was always dealt with), the code they have no longer works. After finding that out they got annoyed, said some things, others said some things, and the topic rambled on a bit before I put it out it's misery by saying:
"Topic closed".