This is the way I understand it, but I am not a medical professional by any means
With LEMS the antibodies block the calcium channels so the problem is that I can use a muscle like to bite down on something but then the opposing muscle will not work because it runs out of available calcium, so then I can't open my mouth to even spit out the food that I can no longer swallow. My tongue freezes in place when I try to move food around in my mouth. If this happens at the same time that I have already swallowed something, it stops in my throat at that point, and I have to try to relax as the muscles spasm and hurt and try to get the food down. It is very frightening. While this is going on my heart is racing, I am not sure if it from the anxiety or the disease, because it does this when I am not trying to swallow or chew, too.
When my breathing muscles clamp down, I have to concentrate on breathing, and my chest wall just barely moves. After the episode passes the muscles release and I can inhale deeply again.