Find file type recursively and move

Hello,
I supposed that it was working fine but now I see that it's not working as expected.
I am running under ubuntu14.04, trusty.

My plan was to search folderA and all subdirectories and move any txt file to destination folder, folderB :

find /home/user/folderA/ -type f -iname "*.txt" -exec mv --backup=numbered \ 
-t /home/user/folderB {} + 

Now I see a new folder was created ,by another process, under folderA , named folderC and it contains multiple text files but the script does not see txt file.

What could be the correct way?

Many thanks
Boris

Hello,
After a couple of tests, I realized that there were some colliding applications over the same folders. So, I have just sorted out now.

Many thanks
Boris