Hi Gary,
The issues you experienced are not expected and I would recommend you to first to proceed with basic checks: https://support.pix4d.com/hc/en-us/articles/115004119343. This article helps users to troubleshoot app issues in most cases.
Another user reported a similar issue, DJI Matrice 200 Pix4DCapture iOS11.0.2 Circling at the end of Grid Lines During Flight Mission, which was in the end resolved by upgrading the firmware of the drone and the version of the device,
I would also recommend you to double check if the sensors on the drone are working optimally by performing all the necessary calibrations in DJI GO 4 app.
Best,