I was told the upswing tongue on the original Trilliums was formed by bending the frame members. In bending, the steel was "stretched" making it thin in places and prone to breaking.
To form each side of the tongue on the TrilliumRV version (which later became the Sidekick) three separate pieces, cut at angles, were welded together. On my 2010 the three joints that form the side of the tongue were each strengthened with two gusset plates, one on the inside and one on the bottom. These additional reenforcements seem to have been abandoned when manufacturing was transferred to Great West.
TrilliumRV used 11 gauge steel (about 1/8" thick) for the frame. Before you have your frame repaired you might want to measure yours. This will let you better decide if replacement or repair is the best option. While I've seen repairs like this done with the body on, I would at the very least raise the body to allow for a more robust job. A trailer frame shop can best advise you. Good luck.