There is an inherrent weakness in the Morgan design - the originals did not have sufficient material and were inadequately supported. The constant flexing of the bracket by the operating of the suspension is the problem, the bottoming out just makes it worse.
Imagine a one foot piece of 1/4" steel clamped at one end in a vice; then pushed and pulled repeatedly back and forth. It will over time weaken and eventually fracture. That's what happens to the bottom bracket. Increased material thickness, three bolt fixings and a welded brace to the axle end will resolve the matter.
