Phantom 4 Pro Pix4d Mission Problem - Hovering

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#1
Our company has recently purchased a second (factory refurbished) P4 Pro. Our first worked well with Pix4d for many flights until an unexpected power loss on descent at the end of a Pix4d mission. Our second P4 has only successfully completed a mission once, after several tries and on different days and locations. In some instances the aircraft gets to the start point and remains there (flying in a small circle and eventually steadying itself), in other cases it completes one row of photos and remains at the end of the first grid line. It also does not travel to the start point in a straight line (the one successful mission did), and in one instance it overshot the start point, then turned around to get back to it. Once on a grid line the flight path does seem to be a straight line. In some cases precision landing functions as it should, but in other cases it lands several feet from the launch site. Initial setup of the P4 Pro included an update to firmware 1.05.06 as well as the usual compass and IMU calibration. I have since downgraded to the previous firmware and there was no difference in the aircraft's actions. Compass and IMU calibrations were re-done several times with no change to the aircraft's actions on the missions. It seems that if we wait for about 1 minute when the hovering occurs the aircraft will regain its bearings and continue with the next line of photos, but the hovering occurs again at the end of each line. We have flown dozens of Pix4d missions with our first P4 and had none of these problems.

At this point we need to know if these issues are due to a failure with an aircraft hardware component, or if they are software/SDK issues. Without a second P4 on the same firmware it is not possible to do any further testing. We have also tried a second capture app (Precision Flight) and it produced the same hovering issue after completing one line of photos. DJIGo4 does not give any warnings of interference, and compasses/IMU appear within the normal values for all of our flights. Satellite numbers were normal during each flight.

We are using the latest Android version of Pix4d, on a Lenovo Tab4 with Android 7.

Any help on this issue would be appreciated. I have come across a few other posts from others that have experienced this problem, but I cannot seem to find any actual resolution.
 
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Meta4

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#2
It also does not travel to the start point in a straight line (the one successful mission did), and in one instance it overshot the start point, then turned around to get back to it. Once on a grid line the flight path does seem to be a straight line. In some cases precision landing functions as it should, but in other cases it lands several feet from the launch site.
The Precision Landing issue might be as simple as a site that doesn't have a good recognisable pattern/texture for the optical technology.
The other issue is hard to work out.
It sounds a bit like an intermittent GPS hardware issue but I can't quite match the symptoms.
If you just do a normal test flight with DJI Go4, does it also have problems?
If so, the way to work out the cause would be to post your recorded flight data from a flight that has these issues.
 
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#3
Thanks for your reply. The precision landing failures I believe are related to the same Pix4d mission failures, because we lift off from a ground control point target with an easily recognizable pattern, and have had zero issues with our previous P4. Precision landing with our current p4 has been intermittent. On our last Pix4d mission we had the usual hovering/circling issues at the grid line ends, but oddly the precision landing worked fine.

I have not yet had a chance to try a test flight with Go4, but when the weather improves I will give that a try and review the flight logs.
 

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