You have seen this 3 times? I haven't heard of this before at all and I can't really find any reference of this happening anywhere online. (not that this means much, i know people don't go posting every time a failure happens). Do you think it is worth the unsprung weight adding brackets? How hard a hit did they have to pop them? Is this perhaps partly due to worn tie rod bushes causing stress in the bolt?
I'm just wondering how much preventative maintenance could solve for this rather than bolting on weight there. It seems like a decent design, but you have me thinking now about this as a risk about a month out from another trip with plenty of rough stuff.