So I purchased a spare Phantom 3 battery, and noticed that it fits the battery compartment a lot more tightly. In fact it goes in, and out, with considerable struggle. Also, when inserting, it does not produce the click when the latches catch on, probably because the whole process is rather hard, and the last few milimeters are the toughest to push in. I flew without issues, but am concerned about damaging the connectors when pulling in or out...
Was there a casing redisign to fit the compartment more snuggly?
The battery is original DJI OEM, purchased from Amazon.

I think tolerances on the plastics are not as good as they should be. Certainly any new battery better be able to be used in any P3.

I had a similar problem a few weeks ago with a battery I bought from an authorized dealer through Amazon. It was a bit tight to insert, but the release latches were so stiff, almost impossible to depress, so it was a painful 5 minute struggle to get the battery out of the bird. After doing this a couple of times, I returned it to Amazon for a refund and bought a replacement from another store (also through Amazon). You might consider doing the same thing - Amazon's return policy is great.

My battery that came with P3 was snug at first, seems to be a little better now.

Well, I've asked for a replacement, or a refund. I used a caliper to compare the new battery to my existing ones, and the casing is 0.5mm thicker (as measured just below the latches), which explains the difficulty fitting it in. The battery (if anyone is facing same issue) was manufactured in September 2015.
I am actually wondering whether this is a mere manufacturing defect, or in response to reports of drones falling out of the sky due to poorly seated batteries? Apparently uncommon, but I've read such statements in this forum...

Their batteries are terrible lately. The tabs don't work correctly on 2 of the last 3. (I have more than 10). I couldn't send one back to DJI, but I could send them back to Amazon.

Wish I had better things to say about DJI... but even their batteries, which I praised highly in the past, have gone south... can't get them out, just for a 5 cent part, which is an easy quality control issue which seems is non-existent.

Long story short... Battery tabs are bad and do not depress correctly.

If they become like... well, add "boring" to the name.

Fat City Posted at 2015-11-7 15:03
I think tolerances on the plastics are not as good as they should be. Certainly any new battery bett ...

I have the same problem with one of my batteries.  I realized for my battery that if I too a key and pressed on the top latch at the very end just a little it would release.  It had to be right on the end to get it to release.  If I don't do that it is almost impossible to get out.  So now I use a small screw driver I keep in my backpack.

I think this ill-fitting battery is more than mere annoyance. I'm afraid the force required to push it in may crack the shell. I'd rather avoid it...