How can I fix the background when it becomes distorted?
Make the changes that you want to the body. Then use the "drag" tool to make gross changes to the background (roughly re-align object etc.). Then use the "repair" tool to fix and small distortions. Alternately, you can use the "revert" tool (select the repair tool and hold down shift) to move parts of the image back to their original positions.
If this has not answered your question, open a support ticket to submit a question to our support staff.