Not sure what all you did to repair the fiberglass or how bad it was, but definitely sounds like air bubbles working up from the repair.
Did you start out with resin & matt for repair or was that all previous? Very easy to get bubbles internally & can take years for it to show up sometimes. After first stages of repair extra heat & dry time help the resins to shrink closer to where they will stay & help hidden bubbles to hopefully show themselves.
But moving on now, that's par for the course for fiberglass & it's hard for you to be 100% responsible for what lies beneath. As you of course know, area would need to be stripped. Then picked at for spots coming loose or revealing bubbles. Then it can be filled, much preferably epoxied, plenty of dry time with some extra heat, & then sand & paint.
This of course is not only a lot of time for you, but to do as good as possible, a lot of downtime for a money making vehicle.
May want to explain to friend & see if he can live with it.