Bike computer stops

Hello, when I use my bike computeur, especially when I download a track, after a while (usually more than one hour), the speed on my screen is at 0. It's not the auto-pause mode.

If I don't touch anything, it stays like that until the end of my ride. So in order to have the speed for an other time, I have to swith off the device and swith on. It's of course not easy and most of the time, this problem appears again later.

Thank you for your help. Cyrille