Apple pulls half-baked iOS 12 beta, as iPhones lock, freeze and crash
The beta eventually catches up with the memory management or whatever bottleneck it's been causing, and the issues resolve themselves, but instead of leaving you to grind it out, Apple just pulled the beta to investigate the culprit. Long story short, if your iPhone or iPad got slow as molasses while you were thinking you are using the latest and greatest pre-release candidate of Apple's newest iOS 12 update, it's not it, it's them.
Well, that's why they call it beta, yet we are getting awfully close to the final release in a month or so. Apple has also taken the file off the Update Center database, too, so yours now has a vintage feel to it.