Looking at the photo of your TT in your avatar, your axles look to be badly shot to me. That could account for the rivets that are pulled out. Look around your TT and see if you are missing other rivets, inside, for example on the ceiling and walls. Your rig looks nice though, a real keeper!
Bad axles are hard on your trailer and will hurt it. Be thankful yours only has one, less $ to replace it!
When you have the belly off (yep, it looks shot, too) have a real good look at the frame and make sure all is well with it too. You won't want to take the belly off a second time if it isn't...
ps: when replacing it, make sure you get the proper rivets, they have a much bigger head and look rather like tiny li'l mushrooms.
If it's to be, it's up to me.