Unfortunately this is a problem that will get worse and is virtually impossible to fix permanently. The fiberglass siding on motorhomes just can't tolerate extreme heat and sun. My previous Monaco motorhome had vinyl graphics over the gel coat exterior and the ones that were dark colors were cracked and peeling badly. When I removed them I found the fiberglass underneath was cracked severely too. I made the rounds to several body shops that repaired motorhomes and the shop owner that was most honest (and also the most expensive), that the only way to fix it with a better outcome would be to grind the the crack down to its depth, feather it out and fill it with filler. This is very labor intensive and it takes a lot of work to do it right. He said even then they might come back eventually. I didn't want to spend a lot of money on this so I elected to have the cracked areas sanded and the cracks filled with filler and filler primer. My Monaco sat outside and I didn't have a cover for it, and within 2 years all the cracks all came back. My neighbor down the street had a 45' 2008 Monaco that spent its life outside and the side that was exposed to the sun cracked badly in all the dark painted areas. He was told the same thing I was when he was going to have it fixed, and when he built a new home he built garage to keep it inside. I have seen this problem in a lot of other motorhomes I have looked at, irregardless of the brand. The fiberglass just can't take the heat expansion and contraction in a hot, high UV full sun climate. I don't know if the newer motorhomes have improved in that area but I doubt it. I am also amazed that the latest trend is to paint more dark colors on them. I notice yours is cracked in a dark painted area in an area of stress where the awning fastener penetrates the fiberglass siding. If they'll warranty it I'd have them do it again, but instruct them to take more material off and feather it out before applying the filler. They might also check to see if the fastener is over tightened, creating more stress in that area. Once fixed, keep it under a roof or cover whenever possible.
Here's some other discussions of the problem that I've found: