Edited to add:
Okay, looking at the photos, I would say that a PO has definitely tried to stanch a leak around those vents, but did so in an improper way. Those would be my first suspect and there is no way I would do anything more drastic before I re-bedded those.
One of those gelcoat chips does also look kind of large, so it is possible that you have a leak there (if it is also penetrating the actual fiberglass), but the vents still need to be re-bedded.
You might be able to check the integrity of the 'glass by taking down the Ensolite and then looking at the fiberglass at night with a strong light
. That might show if you have any cracks or holes that penetrate the shell.
Also, has the roof sagged? I might be seeing a sag in the second photo, but it's really hard to tell for sure. If that's the case, flexing could be another factor (but I'm not saying it is as I can't tell). Can you show more of the "strange steel rod"? I wonder if that was put up top to keep the roof flat. Was there perhaps a heavy air conditioner up there? Or just a lot of holes for the numerous roof vents? I'd like to see more of that rod and the roof, myself.
Again, I would fix those vents no matter what. If those hadn't been leaking, I highly doubt there would be caulk globbed all over them (ineffective, but people do it often).
Okay, what I wrote before looking at the photos:
I would say it's very likely to be leaking from around a vent, and pretty unlikely to be leaking through the actual fiberglass.
As to the leak coming in at an Ensolite seam, that's probably because water is running behind the Ensolite (coming in somewhere else) and then finding a handy ingress point at the seam. Like on boats, the water often comes in at a point seemingly unrelated to where it originates.
Since the vents are very often leak culprits, if it were me, I wouldn't begin to consider/repair more exotic leak sources until I had re-bedded the vents. Especially if there is any evidence of anyone putting caulk or sealant around the outside of the vent flange (this is generally someone's misguided or "shortcut" way to try to repair a leak, so it's likely to mean there has been a leak that has been "repaired").
What I would do is remove the vent, clean/solvent wash the flange and the area of the camper roof that is/was under the flange, and then re-bed the vent with the sealant under the flange (not on top of the flange and its fasteners).
Given that you've had a number of leaks
, re-bedding the vents won't be wasted effort, and then you can see what's what after you're done.