That's a really low cycle failure. Must have been a flaw in the material or the thread-cutting or something, otherwise all of them would have had similar incidents by now.

I'm not up on my galvanic reactions, but I know it's not a great idea to bolt steel directly to aluminum. However, is stainless steel OK? These rod ends are stainless, aren't they?

 

3 failures kinda scares me. I'm assuming this is somewhat of a low volume product.