Sounds like those kegs were infected. Don't cornies say not to exceed 150 psi? Basically they are steel bottles.
Not cornies. Mini-kegs. They are MUCH thinner steel, as they are technically disposable.
I've also pinged one out injecting it with a small CO2 cartridge, so their ability to withstand pressure is substantially lower than a cornie. The tap stayed in just fine and all that holds it is the barbed fitting, but the bottom popped out on the keg.