Almost lost a wheel

Based upon reading 72bluNblu's observations, the other three adapters and studs could be accidents waiting to happen.

May be a good idea to replace the studs in the other wheels and make sure the lug nuts seat properly in the adapters.

At least you would be sure they were not over torqued and unsafe.

Yeah I would definitely be replacing the rest of the OE studs. It could be that the corner that failed had just been over torqued previously and the others have not, especially since it's the LH thread side, but there's no way of knowing that.

And if he can find the right studs he can use the right lug nuts for the adaptors, win-win.