I have this same bubbling on mine from the factory. I think it's normal that it happens. Everyone said to leave it alone and all will be fine but I couldn't let it go. I found that many people suggested covering the lap sealant with eternabond. So I did. I would suggest the same once you know it has cured.
"Take The Road Less Traveled"
2013 Rockwood Roo 233s
2017 Ford F-150 EB
I've been an RVer since 2007, Lifetime Camper
Gotta love the Outdoors, Disconnect and Enjoy Nature!