Gel coat is interesting stuff.
Blooms a lot when older. And easy to get stress cracks.
Jayco are known for it.
And roofs falling in/sagging, walls splitting.

If walls "crazed".That's the gell "flex cracking"
and leaving lines/splits in the Gel..

either stripping back and repaint.
or some sort of filler and fairing will do it.

Best way would be to sand it all off with orbital, or maybe stripper.
and repaint with an Epoxy.
Otherwise. apply filler over any/all cracked areas.
fair back.
Then repaint WHOLE van.

You will NEVER get a full colour match all over
with old coatings.

Unfortunately NO Gel in a single pack is waterproof.
Basically 2 pack and/or Oil based only.
As Jayco and others found out after first few yrs.

All proper Fibreglass layup items, whether yachts. vans, body parts, etc.
Are laid up as the glass, with maybe a special mix of resin the first coupla layers.

Then spray painted with epoxies after poppingoff/out of, mould.
(Gel is for cheapness and speed only).

I've worked on them too.
Popping ouit of and turning over the moulds when on the cranes
That was interesting.
you wouldn't believe the "bouncing" and such we had to do to pop some mouldings out of
"not properly coated" or poorly designed moulds.
I've nearly flipped the smaller cranes on some of them,
Bouncy. bouncy. Jerk. Bouncy, bouncy. POP..
If you lucky.
Those Cole 23 and 30,s were a prick down in Adelaide. (Bink,s Yachts).

Cracking of gel coat is a symptom of UV break down (poor quality gel coat). It should last 20 years, or more. "Patching" it successfully long term is unlikely.
The only effective solution is to grind it all off, back to the fibreglass, and re apply it, or another coating.

Cheers,
Peter