Seam sealer fail - help

Ok so few weeks back, I tried a 3rd coat, smoothed it, then primed it with filler primer, a few coats. Looked like it was going to do the trick. Few days later I notice the caulk is flexible, too much so, if I lightly push finger into the seam , it makes a dent? I cover the car and leave town for a week. Now today I go check it, and now it is bubbling up and if I push finger it now tears and wants to come off. So I ripped it all out ( so fun) and now need to try the 2K stuff. I am already down $45 in the Dynatron stuff, and then $30 for a can of Epoxy primer that I used first, then another can of filler primer $9.

So this 2K stuff, how many tubes is it gonna take? These drip edge rails are pretty wide, and pretty steep towards the back. Eastwood sells a gun and 1 8oz tube for $45. it is 2K and blue. help is appreciated. This is completely hanging me up to get the car painted. all the other body work is done.
Go to your local automotive paint store and ask them about the products they have available. You'll need a gun for the product you choose. Maybe they
will let you borrow one or you may have to purchase one. Yes, more money and the 2 part products aren't cheap, but you will have a gun for future use.
SEM, Fusor are 2 brands and there are others as well. Buy 2 tubes, ask if you can return one if you don't use it. This should eliminate product failure and
you should be happy with the results.