I've owned 3 DJI Phantom 2 Vision + and all 3, at one point or another, have said to themselves, "That's it.... I'm done!" and will come crashing down to earth and I'm out $600+ in repairs to fix the camera.  My current Vision +, which I've owned for 2 months, have had less than 10 flights because the rest of the time it's down for repairs.

With the Inspire 1, how can I be assured that, if the Inspire desides to quit flying and crashes, how can I be assured the 4k camera will be protected??

Very simple don't  buy one.

Ive had great luck with both my Dji phantoms .
I see no reason to test the range I fly conservatively always in range of sight,and calibrate the compass before flying,and lock in a home point ..never an isuse with close to 100 flights.

Do you live near power lines? EMF may be the case here.
Even flying with 6 sats locked in I've had no issues flying if flight was needed .Did you calibrate both the drone compass and remote control by interfacing with a pc? Firmware update too?

Man bad luck ....