I'm a long-time DP, but new to the drone world. Occasionally I am getting what I called "warbled" video out of my drone - a Phantom 3 Standard that I purchased used from B&H.

You can see what I mean in this clip here - particularly if you pay attention to the tree on the left side of the clip, around 2-3 seconds into the video...

Phantom3WarbleEx on Vimeo

Any ideas what would be causing this? I'm clueless and not sure if it's something I can fix or have fixed with the equipment - gimbal/propellors out of balance, etc.? or something that's going on internally inside the camera... It seems to be an intermittent problem.

This is rolling shutter and caused by a vibration problem. While you could drive yourself crazy trying to fix this minuscule bit of vibration during flight, the best way to fix the resulting issue is to use an ND filter to lower your shutter speed and introduce more (good) motion blur to the footage. There are many ND filters available. Try a ND4 or ND8 for general outdoor work, or ND16 for extremely bright days.

Nate, thanks so much for the info. I purchased a set of ND filters for my Phantom recently so it's great to know I can put them to use for a work around. Thanks again!