Yes, that sort of trouble is almost guaranteed. There is no standard for awning mounts, so even changing the awning model within the same brand is highly likely to use different hole locations. Further, it's possible that the RV builder placed backer board in the sidewall solely for the purpose of mounting a awning, meaning the brand & model he planned ahead for.
Get the install instructions for the brand/model of your choice and check carefully in advance. BEFORE you buy the awning.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC