Has anybody noticed weird behavior and/or loss of communication with drones of any kind in mountainous areas? Have you been unable to get your drone to cooperate with normal commands like "come home NOW" OR "return to last waypoint"? Has your drone taken off, hit a few waypoints and ignored the rest?

Keep in mind I'm talking about mountainous areas...I'm a newbie, so I apologize in advance that I'm unaware of signals from other sources bouncing around mountains and causing a problem, if that's the answer. I'm just curious about other people's experience in not-flat terrain. I would also add in some sparse (very rural) population, possibly people with cell phones, ham radios, etc....would this cause problems?

Thank you and happy Friday!