My 3 years old 13'' MacBook Pro Retina doesn't sit flat There are 4 rubber feet on the bottom of MacBook Pro. They worked well before. But recently 2 of them (near the touch pad) cannot touch the flat.

I phoned Apple support and she said that this is most likely because the battery is bloated. And she suggested me send my MacBook to the Genius Bar for repair.

But I use several battery status checker apps, such as coconutBattery, battery monitor and the built-in one, they all say my battery is good.

So what happened?
I had a similar experience with my 2013 MacBook Pro. The battery was bloated causing the MacBook to wobble even on perfectly flat glass.

Battery checker apps like CoconutBattery were reporting it to be normal. Even macOS wasn’t showing any battery warnings (I have consumed only a reasonable number of charge cycles).

While the cause of bloating still remains unknown to me, Apple service recommended me to replace the battery as the continuous bloating may end up causing damage to the board, bottom case, trackpad and the keyboard.

It is advisable to get the battery replaced as soon as possible.

Note: After getting the battery replacement, I sought advise on do's and don't from the technician. I was told that this wasn't an expected behaviour and happens in rare circumstances. Thus, the cause for bloating remains unknown to me.