"Banana" alignment

Hello, from the elaboration of a survey carried out with UAS I get a “banana” alignment. Any suggestions to avoid this problem? Thank you

Hi Walter, 
regarding this issue we created this article: https://support.capturingreality.com/hc/en-us/articles/360018811880-Banana-effect-what-to-do-if-my-model-is-bent

Thanks, I tried to solve the problem in post production as indicated in the article, unfortunately without any success. I will try to return to the field and acquire new images and GCPs.