Maybe you did not "butter" the ceramic blanket before applying the refractory? Then it may have delaminated to leave it hanging in a 3000 degree breeze?
"Buttering" is spritzing the blanket with water so that the face of it is not so dry that it sucks much of the moisture out of the refractory, causing problems.
On the third burner, when you had it off, did you leave the choke fully open or closed? I learned with my Mr. Volcano to just remove the burner immediately upon shutting the burner off. Yes, I melted the gas line off. I had it partly closed off with the choke open. I was cleaning up and soon found the gas line on the floor, melted off from the fitting at the burner. The instructions tell you that the forge should not be closed off and the choke should be closed. Nevertheless, I just remove it immediately, as it is held tight with a thumbscrew, which makes for easy, quick removal.