, As it was explained to me from GoPro, they say if you fly in an area with interferences, such as houses, buildings, cars, radio towers, power stations, power lines, etc..., basically anywhere but an open field 100 miles from civilization, you have greater potential for losing GPS and the controller connection.
Anytime you have a new technology, there will be a learning curve. Cell phones for example were highly volatile with poor coverage and features for several years. Same here, you have what is a pretty amazing product in these drones, but it is still in its infancy. As you said, all drones, even the mighty DJI has these issues.
Obviously it is a stretch saying " in a field 100 miles from civilization", but the fact is you should not be flying in populated areas per the FAA. As you said, there are numerous RF per the items you mention with the big one being communication towers and power stations; and there are more around than you think. Additionally, everyone has wireless networks and other systems flooding the airwaves. Demand drives technology, so like cell phones, they will get the frequencies right on these drones, but when you are looking for "cutting edge technology", that is what you will get unless you wait for it to take really off. Punage...
Either way, I have had my Karma a few months now, and really only had one blip in compass issues when trying to launch from a sunken area on a cliff. Moving the drone a foot corrected it. I don't fly in populated areas. Many hours of flight and no GPS issues, fly aways, or anything like that. No doubt there will always be failures, but most videos I see are pilot error, being unfamiliar with the drone, letting the battery get too low, flying outside of FAA restrictions such as line of sight, and yes where they fly it being in urban areas. Fly it in between tall buildings and you are going to lose GPS, fly it behind a building and you will lose connection to the controller, fly it in populated areas and you will have interference, do not set your return to flight high enough and it crashes. You do seem to get a lot of negativity on the Karma because of the recall, but it "does" appear the issue has been resolved with a new battery mount. Unfortunately, now the issue is "perception" or "fear". Either way, in all the time I have flown, I have never had any of these issues, however when I first got the drone, I tested how it would react in these stressful situations by putting it in an auto path and shutting off the controller, letting the battery drain so it would return to launch, moving a great distance to return to me, and canceling these RTH modes to retake control. I have not been able to test the loss of GPS because there is no way to cancel it, though at some point I will find a big warehouse, or take advantage of a situation when the error occurs and test that too. Either way, if you get familiar with these drones, and you know what to expect when something goes wrong, you not only will be more confident in the drone, but better prepared to handle a stressful situation and hopefully not post a YouTube video of your crash where "perception" and assumptions mostly by DJI owners cite a bad product, though anyone looking deeper recognizes one, maybe many errors you made that caused the crash.
BTW, I practice a lot, not just to get a better feel for the drone in good and bad conditions, but equally as important video composition. One item I am always working on is landing on a dime, even sometimes using the camera to land at a distance. I do this whenever I practice since many areas I go such as on my boat affords a very small landing site. This also helps if for some reason my launch site may not be available per the boat moving, or another emergency forcing me to land the drone quickly. Either way, all this practice not only helps get better video at the time it matters, but also affords me more time to shoot video since I am much more efficient in both flying and video composition.
To end my diatribe, the most crashes I see are from pilots even admittedly being unfamiliar with the Karma, be it not reading the manual, failing to adhere to the FAA restrictions, or pushing the drone to far beyond its or their own limitations. You also see so many pushing the battery to capacity which will force what many describe as "losing control" when in fact the drone takes control to land per a failsafe. In that regard, like any electronic device, especially photography, I always recommend getting multiple batteries. This helps ensure you keep good habits by accepting low battery warnings and don't push the drone beyond its limits...