No cell coverage saving project in field no working

Today I was working in a no cell coverage area, or very weak signal at times and was unable to save my planned mission.  The mission could only be planned in the field since I had to fly stockpiles for volumes measurements.  After walking the perimeter and putting GCP's, I had my mission planned but then couldn't save it.  The purpose to save it is to shut down MP so I can use DJO go to start flight checks, then go back to MP and open the mission.  This did not work at all.  I had to re-walk the perimeters and create a new plans, this time I did not close MP but left it open and started my flight directly from MP without using DJI Go first.  This was the only work around but not ideal.  The mission would start to save and get about 3/4 done and then just stop there without progress.  Waited for several minutes and then gave up and cancelled it.  Tried a few times without success.  There was no warnings or popups at all.  Any idea why this is happening?