.... Ive made sure all settings are correct...
...When hiking I close my screen with viewranger open and on the screen. When I check back it has gone into the app tray. When I open it again it has either jumped to my current point in a straight line or finished my track and started a new one by itself....
Do you mean the settings in ViewRanger or your phone?
When I installed VR on my "dedicated GPS phone" I had this problem. All the time VR was active on my screen it was okay but as soon as I locked the screen or had VR running in the background it got stuck and did the same as you mention - jumped from my last logged location to my current location.
Turns out I needed to change the settings on my phone (not VR) to allow "open" apps to run in the background when the screen is locked.
Might be worth a poke about to see if there's something like that you can change on your phone.