Problem with suspension fork I am having trouble with my bicycle which is a Giant Terrago FS1.
I have posted a video on YouTube which might help to explain the situation better, as it might be better than words.

Due to the problem, my handlebars wobble and the suspension doesn't work. However, if the fork lowers are pulled forwards as in the linked video,  the suspension will work. Does anyone have some clue regarding what might have happened?

Here is the link to the video: 
                
            

If you need any further details please do let me know.
This is usually due to excessive wear on the bushings in the fork lowers. There is no rebuild kit for that fork that I'm aware of so, your best bet would probably be to replace the fork or if you can get your hands on a second-hand set of lowers for this fork that are in good condition, you could swap them straight over. If there's that much wear on the bushings though, there's probably a build-up of rust on the stanchions abrading them so it'd be better in the long run to just replace the fork as a whole.