Camera Position Changes during alignment

I took images from a height of 7 m using Sony alpha a51oo 24.3mp camera mounted on drone. 

When I wwant to align all the images, I found some camera position and its point cloud are in different position (attached photo)

why this is happening??

It also is the same when I used flight log (GPS position data).

Any suggestions, please?

 

use a control point to nail it down