I would not think a telephone would cause you a problem. to many others have them near by when flying.

You fly almost every day and I would guess more than once per day.

So this is happening 1 out of 50 flights?

Do you see your plane making funny movements that you didn't ask it to do?

Do you see it not responding when you have put in small movements?

On your DX8 you can have it show you how many "Faults" and "Holds" occur during your flight. Keep an eye on those when you fly.

The manual tells you what is acceptable and unacceptable. You can have like 50 faults is normal with DSMX but not ok if you are in DSM2 mode.

Let us know what you find.