need Beretta 92/96 advice - locking block - what to look for in worn 92/96's

Sounds like you're in need of a new locking block,the 2 92 fs that I have can move but they haven't fallen off on their own. IIRC the locking blocks should be replaced at 5000 rds.

Regarding Beretta 9X Series guns and .40 S&W - note the buffer in your 92A1 - it was put there for the 96A1. The .40 S&W beats the heck out of the Beretta 9X guns. There is only one gun currently in the Beretta 9X line-up that shoots the .40 S&W, and that is the 96A1.

A locking block is an inexpensive and lightweight part, and which is easy to install.
Worthwhile to keep a spare in your bag of Beretta mags.
If it breaks, just pop the new one in, and keep shooting.

The chances of breaking one during an actual firefight are probably about on par with with being bitten by a shark while taking a leak on an electric fence in a tornado.

I've heard that they can break. I've even seen pics of it on the internet.
I've never witnessed one in person.

While you're buying spare parts, always a good idea to have a spare extractor, extractor spring, and firing pin.
Those parts can each be destroyed by one bad cartridge.
I have seen extractors and firing pins get toasted.

Some locking blocks come off the barrel pretty easily. I would closely examine the entire block, especially the "ears" for any sign of cracks or deformity. As was said, it is not a bad idea to buy a locking block kit (which comes with a recoil spring) for $35 and keep it on hand.

5000 rounds is a commonly recommended service interval for recoil spring replacement. Few would routinely change a locking block short of 15,000 rounds.

One of my Berettas it comes off easily. Circa 1996 production.

The other one it is hard to get it off. Made in Italy 2014.

Both shoot accurately and no malfunctions.

So there is your answer.

Same as BSA. I have a 92 and a 96. On the 92 it is difficult to remove. On the 96 is slides right out. They both work fine.

I would not lose sleep over a loose fitting locking block. Turned at a certain angle, some will fall out on their own. Sure, the 40S&W puts more stress on it, but just inspect the locking ears for cracks and replace as necessary. If it has a lot of rounds through it, that would be one thing. But since you said that the finish isn't worn off of it, it sounds like one that is just loose. If used enough, you should be able to see finish wear on the "nose," the end, and the ears - those are the contact points. Another tell to the approximate round count is how much finish wear is on the aluminum frame rails.

Some fall out easy. Some don't. I have broken some and replaced many more that other people broke, from 9mm M9 pistols- not the more powerful 40. Not a fan for this and other reasons. No more to say on the subject.