Should I Eternabond or lap sealant

Clean the area with alcohol (denatured) and apply some sealant.
I'd probably go with Dicor self leveling LAP sealant. It's UV resistant and if your issue is up top that might matter over time.

Unless there's a structural reason for more lateral hold in the area. Then the Eternabond might hold things together better.

Just my opinion.

With our Bounder's front and rear cap seams. I scraped off a few areas with distressed caulking; cleaned the full seam with acetone; applied fresh self leveling Dicor; covered the seam with one piece of 4" wide Eternabond; placed a bead of non self leveling Decor seal along the leading edge of the Eternabond.

We kept the Bounder for 4 years, and sold it to a neighbor about 8 years ago. Looked it over about 5 months ago (Helping him replace a fantastic fan.), and the caps seams Eternabond cover still looked goo. Dirtier for sure, but no puckering, or signs of potential water leaks areas.

I consider these steps to be almost a 'one time maintenance' area, by using both the fresh sealant, and Eternabond coverage. (Reality, some day in the future, suspect this will require a second coverage with probably overlapping two long pieces of Eternabond. But that 12 year old job did not seem to need any attention...:)!)

Best to all,
Smitty

Eternabond, it's a one time repair. I also sealed my front and rear caps on our 96 Southwind with Eternabond about 10 years ago.
It has been leak free and when I wash it the Eternabond looks new, it holds up very well.
I seal the edges of the Eternabond with Dicor, it's not necessary but, I do it anyway.

FWIW: Since we discovered Eternabond, it's been a one time repair for us after several years of always going up on the roof removing and recaulking/resealing.

Did all our seams, and around every piece of furniture up on the roof, ladder attachment, antenna, skylights, fans, absolutely anywhere that could ever leak we put some eternabond. We also after much frustration cut a very thin strip for around, the windshield edges that we tried for several years to stop leaking including reinstalling to no avail. Eternabond did the job 2+ years ago and it's still working, and I don't think we'll ever use anything else but .........

PS: We've even used Eternabond around the outside of stucco building cut outs for pipes, and it's worked super for that use as well, keeping any bugs/rodents etc out.

I'm definitely a BIG believer in Eternabond. I had some leaking coming through the roof at the seams on my 10 year old RV. I simply used the cleaner that is recommended to prep the areas and then applied the Eternabond tape. The entire job only took me about 2 hours to go around the entire roof on a 30 ft RV. It solved the problem immediately and 2 years later I have absolutely no leaks. I would recommend getting the widest Eternabond tape. I think the one I use is about 5 or 6 inches wide. I also highly recommend keeping track of all your repairs and maintenance using an excellent program called Automotive Wolf car care software. It lets you keep a detailed vehicle maintenance log. I also this program to manage my generator maintenance on my RV so that I remember to exercise the generator at least once a month to avoid problems.

If that spot is fairly level, it is an excellent candidate for clean up, apply dicor self leveling and forget about it.

Not knocking eternabond, it has its places.

Self leveling can self level itself right over the edge and down the side of the unit in certain circumstances including high heat, so, I'd recommend using that toward the middle... This was a suggestion from the repair team at my dealership.