Swampman,
Yes, reloaders and shooters often cause themselves problems.
The 788 with the sheared off bolt lugs was due to a combination of issues, poor fitting of the bolt lugs, lack of a back up lug if the main lugs fail and the shooter overloaded his reloads. This is the only rifle I have ever seen with sheared off bolt lugs, something else normally fails first. Just after this happened production of the 788 ceased for good. Most guns are proof tested with high pressure loads, how high most manufacturers want say.
On the Model 7 with the cracked receiver, the receiver cracked with no damage noted to the barrel, the bolt lugs, the bolt face, the receiver locking recesses you expect to see one or more of these damaged before the receiver cracked. The shooter observed no bust cases, no blown primers, no gas blow back from an extreme overload.
Maybe the receiver left the factory cracked due to over torquing the barrel when it was installed? Maybe the heat treatement made the receiver too brittle? Maybe the steel has impurities in it to cause weakness? It is possible to ruin or damage a Model 7 or 700 receiver when removing the factory barrel, barrel removal/installation is more difficult with a round receiver. I had to do a little repair welding on the right rail on a Model 700 due to action wrench damage.
Some of the Model 17 Enfields developed cracked receivers due to over tightning of the barrels at installation in combination with being heat treated too hard over Rockwell 50C.