Have just swapped my Phantom at dealer (less than two weeks old) Video stopped working properly a few days ago. No signal at 20m and 30m. The problem started after a firmware update.
When first unboxed and powered up, day of delivery September 1st, a firmware upgrade was applied. That was before I'd even flown it. It flew perfectly with good video signal. Then around a week ago another firmware update was forced on me and that's when the video problem began. Seems from forums I'm not the only one. I can't find release note documentation that details what the firmware update was for (remote, aircraft or both) and what it was meant to achieve.
The brand new boxed one I got last night won't be getting any upgrades to the firmware until I can figure out how to backup all existing firmware or have access to a working archive for P34k firmware that actually allows rollback. I was unable to rollback last week.
I can't be certain but I suspect that the first firmware updated the aircraft (due to the version numbers I remember) - this is all new to me, my first drone - and the second update was for the controller and coincided with the app update.
Other manufacturers would have a page on their website listing all firmware update details in date order.