MeTV published this piece a while back:

https://www.metv.com/lists/8-minor-mistakes-and-tiny-errors-made-in-leave-it-to-beaver

Well, I must admit I never noticed most of these. Of course most Beaver fans have noticed the age problems with both boys. And I have noticed the record player problem with Beaver's gag. The thread or string on the bee may be more noticeable on the remastered DVD than on TV.

Here are my favorite goofs:

1. The three Gilberts. Originally Gilbert Gates, with a father who's a musician; Gilbert Harrison, in a few season 4 and 5 episodes, and Gilbert Bates, whose father is an electrical engineer.

2. The disappearing lamp post (new house). It is seen often in nighttime establishing shots, at the curb on the left side of the driveway. But many daytime scenes are evidently shot either at another driveway or on the soundstage, where there is no lamp post. It is seen only a couple of times in scenes with the actors.

3. Boom mike in the shot! There is a scene near the end of the series where Wally and friends and Beaver are going up the stairs, and the camera briefly catches a boom mike. An editor could probably have fixed it, but at that point, it was either 'I don't care' or 'I didn't notice.'

I noticed in the episode where Beaver is collecting frogs that there was a string around a frog Wally was going to grab.

Here’s a minor mistake:

In Lonesome Beaver we find that Eddie’s middle name is Clark. Much letter in the Credit Card his middle name changes to a W.

Also re Eddie someone made a comment in an early episode that Mr. Haskell owned a garage, like for car repair, I guess. If so it's unlikely Eddie would have gone to work at Mr. Thompson's service station.

Right and if he did he would be more handy with spark plugs and radiators.

In another episode Eddie says his father’s in real estate. I think it’s Wally’s Orchid. He also says his father knows a lot of rich people.

I love how that article pushes the usual mythology about the "idealized" "perfect" world of LITB. Never mind about Larry Mondello's absent father, Andy Hadlock the alcoholic, Chopper's broken family, Marlene, etc. etc.

The stairway railing/banister of their new house ( 211 Pine ) is barely self-supporting. A few times as a cast member goes to ascend the stairs, the railing can be seen wobbling from just light pressure from their hands.

No one is going to slide down that thing without wrecking the set!

We only see Ward and June's bedroom a couple of times, two times I remember are Wally's party in season 6 (where Beaver rigged the jokes), and the bum visit, Mr. Jeff, also in season 6. In each episode the set construction was different, so the room looks totally different..

Also we've noted before that in a very early episode, probably 'Spelled, Miss Canfield called Whitey "Harold." And near the end of the series, Whitey calls and tells Ward or June that it's "Hubert" calling.

Finally, re Beaver and Gilbert, there is a problem with the credits. There is a Teleplay (rewrite) credit, but no story credit. So the original writer of that episode isn't known, unless there is a script somewhere. My guess is that it's George Tibbles (who shares Teleplay credit with Connelly and Mosher), but no way of knowing for sure. Or, the Teleplay credit should have said Written By.

Also there is one episode where the credits are all wrong. They list all Beaver’s classroom gang like Karen Sue Trent, Sue Randall, Richard Correll, Keith Taylor etc. and it was an episode about Wally.

I think the one that's got wrong credits is Wally's Track Meet. It's right on the DVD set so I think it's a MeTV episode that was prepped wrong. I sent them a contact about it but they didn't do anything to correct it.

One time I complained about the lousy service at KFC and they ignored me.