On a engine with the loop glow plugs, and they are wired serial, is there more than one way that they can fail?

Someone posted a very helpful, how to, that describes the failure of the loop glow plug, in a wired in serial engine, and it shows the loop being burnt with a whole in it.

I am trying to trouble shoot, and would like to be clear if there are other ways that the loop glow plugs can fail.