Your Phantom should be able to reach about 1,000m
(500m CE). When in beginner mode, you'll only be able to go 30m. You've reached 50m, so that shouldn't be causing the issue. And, you won't lose the remote controller signal when hitting that 30m limit.
Here are some other things to try:
- Make sure you're running the latest version of DJI GO and you have the latest firmware installed on your Phantom and remote controller.
- Make sure you don't have any electronic devices on you (other than your remote controller & mobile device).
- Try flying in a different location. Perhaps there is a lot of interference where you're flying.