I do not think this model has a Axle in it. It has a Bushing and Bolts with a Nut in the rear. Most likely the Bolts loosened up and were not tight, I always check those.
Rivet a Aluminum Plate over the old hole, both sides on the outside only. Make sure you use good Steel rivets to fasten it with Washers on the back side. You will have to pull the Skid and I bet you will find more problems when you get the Skid out. Wheels, bearings, Shocks, Slides also check the Long Bolt on the bottom rear. They like to break.
This could be a big project and if you do not have some good Tools to work with and know how to pull the Skid and put it back in, you may have trouble with it.