I've been flying my Phantom 3 for a while, and just noticed a little piece of white 'foam' holding the camera, preventing it from 'rotating' left and right.  This is on the first pivot, just below the aircraft.  The other two pivots are free, and everything seems to work.

Not the bigger translucent Gimbal Clamp, which I removed as on page 7 of the manual (Preparing the Aircraft).

Should that piece of foam be removed?  I cannot find it mentioned in the manual.

Thanks!

Yes, remove the foam piece or the gimbal won't rotate left to right.

The foam piece behind the gimbal was for shipping purposes only. Remove it and throw it away.  It should have had a red sticker on it saying "Remove before flying" or something similar (mine did), but this sticker was missing from many P3s.  You are not the first (nor will you be the last) new P3 owner who did not know they should remove this packing foam piece before flying the first time.

Your video will get a lot better too