Be sure to discuss with the LA person so they are aware of the problem. The fabric has a straight line through it. You will want that to line up close to a center line point at the top and bottom.
I always mark backings with center, top, and bottom reference points for the LA person. It helps to avoid mishaps on positions.
What does the backing look like if you fold in half on the 120 inch side? Match the selvage lines across. What do the side edges look like? Did you leave plenty of allowance and over size the backing?
The video gives an idea of what I'm trying to describe.
https://www.youtube.com/watch?v=EcpzwJMVTbc
ETA: You have some good answers already. I forgot to hit "post" on my reply so it is late.