I'm totally confused.
I concur Kreem is Krap, as its a thick liner prone to separating from the tank, which is what seems to be happening here.
Personally I've used POR15 to great success, as it's a super thin incredibly tough coating that adheres to pretty much anything it touches permanently.
But, let's assume Caswell is even better. Why do you not have to remove the Kreem first? Surely you're not suggesting the Caswell liner is going to simply sit on top of the Kreem? That's clearly a waste of time and effort. I've never used Caswell so I need to be educated.
Now, about this 'clog'. If you can see it and if it's Kreem and if you're planning on removing the Kreem I'm lost as to the confusion of what to do with it. Poke it out - pull it out, drill it out. Whatever it is get rid of it. If it's a chunk of Kreem get it out of the tank.