I've read all the other posts on this, people having isues and then they realise the issue is what they're viewing it in - but this is not the case here - I have a video to prove it.
When I save for web, and select the gif looping option to 'once', when I click save you can see it changing itself back to 'forever', and then saves a continuouslyt looping gif. It took me a long time to notice this, but I finally caught it on video. It only happens sometimes - but is very frustrating as I have no control over this simple command - for it to do as I'm telling - paying - for it to do. I test the gifs afterwards by dragging into Chrome - whoch does show gifs correctly and will show a gif only once if thats how it has been saved (unlike preview which alwasy loops regardless). Video attached...