iPhone 6 and iPod Nano Crash while using PolarM400 with Bluetooth

I had 2 different cases when while running and using my Polar M400 watch and Hear Rate Sensor, two of my iPhone6 crashes and died and crashed while running, today the same happened to my iPod Nano. Each time I had Bluetooth on. First time it was a silver iPhone 6, it happened in early June. By the time I finished by run, the phone was off and it would not turn on no matter what I did. So I sent it to Apple and started using the extra phone I had. Second time, about 3-4 weeks later, I was running again with Polar M400, Heart Rate Sensor and Bluetooth on with my golden iPhone 6. By the time I finished my run, the phone was off. I managed to turn it on, but nether wi-fi no bluetooth worked and the phone kept switchin off. I sent it to Apple and got a new replacement. As this happened, I felt maybe its because of bluetooth, so now I run with bluetooth off in my phone.

However, today this happened to my iPod Nano. I stopped listening to music about 4K down the run, and by the time I finished my 15K I saw the screen was off. I tried turning it on. I did switch it on, however the screen is white and I see a big stain under the glass coming from the left side corner.

Is anyone having the same problem? Am I doing something wrong? Is this the problem on Apple side or on Polar side?