I haven't actually heard of this happening, but I wonder if it could be a "counterfeit" breaker - a cheap knockoff. Did you get it from a reputable dealer? How much did you pay?

David, that is so scary that ANYONE would carry such a product. The liability has to be huge. Why anyone would take the almighty dollar over someone's life and safety is beyond me...but it seems to happen every day.

Suppose you're the purchaser for a nationwide chain of cheap tool stores (I'm not naming names partly because I'm speculating wildly). A vendor offers you a deal on breakers for a common panel - one-third of the usual wholesale price. You can price them at 40% less than the regular shelf price and still make more profit. Everybody wins!

Uh, maybe not. The vendor got them from a broker for a Chinese sweatshop. The broker shipped over a breaker and asked the Chinese company to copy it. (Happens all the time.) The copies were supposed to sell at one-third the price of the genuine article. Chinese labor's cheap, and since it's a copy, design costs are practically nil. So it should be easy for the sweatshop operator to make a profit on this deal.

But the sweatshop's operator was a little greedy. He decided he could make even more profit by cutting corners on the copy's molding. So instead of making a new mold, he had his moldmakers tinker with something similar and get it sort-of-close to the right shape and size. Or maybe he just told them to skip the QA and get on with the next job.

To the broker, the vendor, and the store buyer, the breakers look just like the other ones on the shelf. They might even say "Made in USA" on the copied stamping! But they fit just a bit funny. And the guts are definitely different - but again nobody sees that.

Until the insurance adjuster figures out what caused the fire. By that time the store's stock is gone and the buyer has left the company. The broker is working under a different name halfway across the country. The sweatshop is now making cheap gas generators and has no record of ever having made breakers. So what can the adjuster do?

Did it happen that way? Probably not. As I say, it's all speculation.

Still, similar things happen every day, and not just overseas. After all, it was an American automaker that decided it was cheaper to pay off lawsuits over fatal accidents than to fix a defective design. How many people died? We don't know, because they settled most of the cases out of court.

The dollar is here and now, and a person's life is an abstract concept sometimes half a world away, all too easy to ignore.

I picked the breaker in question up from HD. Got the one in question and at the same time got a 20A single pole. The overall size of the questionable double pole is shorter in length and the area that sticks through the knockout in the cover is also shorter. The breaker went in hard and is completely seated and yet sits at a slight angle appearing that it's not completely seated. The 20A single was fine.
I think I will pull it and do some very careful measuring and compare it with some others. I might call Siemans to see if they've changed something. But, if the breaker size specs were changed, I would think that the model number would change.

Are you sure you got a double pole breaker? Is it possible you picked up a tandem breaker by mistake? A tandem breaker, when trying to install where the bus is not notched, will sit at an angle as you describe. A double pole breaker will have two handles tied together and occupy two spaces in the panel.