If they were sealed up with the Walker Acousti-Seal stuff, that ERA recommends and use themselves, then it tends to "bake together" a bit. Epoxy it's not, but you will have to whack it with a soft, dead-blow hammer, and it will come apart.
This is the stuff I'm talking about, and it's great stuff too.
https://www.amazon.com/Walker-35959-.../dp/B000CQDL94