Is there a way to downgrade my firmware so that my Phantom 3 advanced will work again? I wouldn't mind going back to like version 1.4 or so. With the new updates, I presently have real problems with video lagging and weak signals.

You can Downgrade only only one step. from 1.9 back to 1.8 or 1.8 to 1.7

Hi, you can go back one version for firmware.

If the issue persists, please contact support@dji.com and we'll help you with it.