For what it's worth, I had the exact same problem and had to squeeze the shell at the end where the battery was catching to remove it. So I thought maybe a part just didn't seat correctly during factory assembly which led to my decision to remove the battery bay. Once you remove the GPS antenna...
I'm in Virginia Beach, VA with a 3DR Solo, two Hero 3+ Blacks, and a Hero 4 Silver. Having a blast zooming around the most eye-catching spots in Hampton Roads, often with my wife and 4 daughters along for the adventure.
As for future drone action, I'm not sure if I'll get a Karma (though I'll...