GPS is, unfortunately a pretty complicated system with a lot of points of failure between the app, the phone, and the satellite network. Why don't we have you downgrade off of the beta version, and if you will try out the current production version of the app and verify for me that the GPS works better for you, it will hopefully help narrow things down to the beta version of the app as the culprit that is causing the GPS issues that you are seeing.
So, here are instructions for opting out of Beta
1. Go to this URL https://play.google.com/apps/testing/com.och.BillionGraves
2. Click the link that says "Leave The Program"
3. Follow the instructions on the page that the link takes you to.
Be sure to upload any photos that you have taken beforehand because Google makes you uninstall and reinstall the app.