Android video footage causes error messages and offline preview

After a hiatus of not editing (when I stopped the video game I was using HDV tapes :-0)

Now back to the future

I want to edit a lot of mobile phone footage shot on Samsung Android.

I've been careful to set the sequence to match the frame rate 29.97 fps.

I'll start the project and all seems fine but very quickly two things seem to happen each time I try to do a project:

* initially footage plays in the source monitor, I import and lay it in Sequence track.  Render the project and it usually plays fine.  If I close the project or work on it for a period the footage mysteriously goes offline. Manually linking the file doesn't solve the problem.

*footage that has been uploaded fine in one instance won't upload in same project and gives me an unsported format or damage file .

Should I give up trying to edit my mobile footage in Premiere Pro? 

Is there something I can do to stop these errors?

Would editing in Rush and pushing it to Premier Pro help?