When you save, I'd advise to do it in the campaign editor window, not the triggers or even the map itself, I've had problems with data reverting because I was saving the map and not the campaign
I do always save through the campaign editor window. When I noticed it stopped saving object data within that map, I tried also to save through the object data tab, and the map warned me about "not all players have starting locations blablabla", so I did that, but nothing changed.
EDIT: So, the update I have is:
There was a pink line under a changed icon that was the same in the Campaign Editor. I thought that by removing that everything would work again; you know, if you try to import the same .blp when the same one was already in the campaign with a different label, then it would read 0kb so you'd have to import it all over again, but nope, that was not the case in this instance.
I've reset some other pink lines and they DO save after the W.E. restarts, but new pink lines won't!!
Fortunately there are triggers that can seemingly help me to create some workaround, and the icons I've changed did get saved a few days ago, when this thing was working.
If anyone hasn't got a solution for this, then my hopes are for next maps to save Object Data alterations with no problem such as this.