Large difference in elevation on stockpile measurements

I recently flew 2 missions over the same site to measure stockpiles.

On the maps that where processed. The one shows the elevation of the stockpile at 20' (flight1) volume at180.98 yd³. The other at 3' (flight2) volume at 1,207.48 yd³. The takeoff elevation is also different. 1660 as compared to 1479.

Mission was flown with a DJI 2s with MPP. Can you please help me figure out what went wrong?

Thanks

FLIGHT 1
Images Uploaded    105
Input GP    2.095995
Output Size    9369 x 9666
@ 0.78 inch/pixel
Average AGL Alt    194.04 ft
Area    8.39 acres
Elevation Range    1462.0 to 1525.7 ft
Info from in image tags flight 1

FLIGHT 2
Images Uploaded    106
Input GP    2.115957
Output Size    9644 x 9798
@ 0.76 inch/pixel
Average AGL Alt    25.30 ft
Area    8.36 acres
Elevation Range    1657.3 to 1666.9 ft

Info from in image tags flight 2

takeoff altitude 1629
flight altitude    1849
flying elev    220