Not sure if this will work for you but I had similar problems when I first flew my
MA2. I couldn't get more than 500m or so away without the signal cutting out to my phone and losing signal with the drone returning to home. A few times it did it I was line of sight with it. Not having owned a DJI drone before I was pretty disappointed with the range.
But after watching a few youtube videos I noticed that in other peoples DJI Fly app you could pick between the 2.4ghz and the 5.8ghz option or put it dual band but mine did not have that option only 2.4ghz was there. Weird. My DJI Fly app version was 1.1.5 which was the current one out when I bought the drone. I uninstalled the app, deleted the cache, reinstalled but it was still like that after the fresh reinstall.
After searching around a few forums I found a thread where someone mentioned having the same problem with a new drone purchase and app 1.1.5 on their android phone. They mentioned they rolled back to a previous app version on apkmirror, connected to the drone and the option was there. Then they let the play store update the app and it then remained there on 1.1.5.
I did the same, installed 1.1.2 version, connected to the
MA2 and there it was, 2.5, 5.8 and auto. Was not there before. I then disconnected the drone, and opened the play store and let it update to 1.1.5. And there the option was. Set it to auto and went and flew the drone. Not 1 dropout for the whole flight where I was getting 3 or 4 for the battery duration previously. Next battery went and flew it further away and got to 2km away before I turned around and came back. Have since had play store update the app to the latest 1.1.6 and the dual band option is still there and done is flying well.
Have used it heaps since and not having any more dropouts or anything. Hopefully it might work for you as I understand how frustrating it was when you could hardly fly it further than you could nearly throw it.
DJI Fly apkmirror link here -
DJI Fly APKs - APKMirror