Colorado Redneck -
To be honest, I really don't know.
I've pondered the same thing, since I still own several Marlin X7s, and there's still at least one Rem 783 in the family.
But, it's a common enough failure that it regularly shows up on the Marlin forums (where people are primarily trying to source parts for less than Numrich prices - for both the X7s and 783s).
Most claim something along the lines of the trigger taking a hit from the side, when being dropped; or catching a cut branch stub while being lowered from a tree stand; or being stepped on. Or, the trigger got smacked during cleaning or other work that required it to come out of the stock.
When I first started seeing the reports, I was an absolute disbeliever. I gave many replies along the lines of "How the 'heck' do you break a trigger housing?!" But as I looked into it more, and saw more reports, I finally just had to accept that it's a bad design and/or bad casting.
It didn't hurt that when I started seeing those reports, I was working on an AR magazine conversion for an XS7 in .223 Rem, and that fire control housing had some obvious flaws in the casting, right around the mount holes.
It's entirely possible that there are bad castings out there, and/or people are over-torquing the screws and cracking the housing.
But...
I wouldn't sweat it, if you have a rifle that you already trust.
My first X7, a 2009 JM XL7 in .30-06, took more big game in two years than any other rifle of mine has over its entire lifetime. I have no plans to get rid of it.
And I recently rebuilt the .35 Whelen that I built on a Remlin XL7. Again, no plans to get rid of that one.
I just won't buy another one.