Frigidaire FEF369CGSB - Strange Cooktop Behavior

I have a Frigidaire FEF369CGSB range that is exhibiting some really odd behavior with the cooktop burners.

[list=1]*]The left-rear and right-front elements always work.
*]The "Expandable Element" center segment will not heat, ever. The outer portion will, however, if it is switched on.
*]The right-rear element will only work if one of the other three elements is also switched on.[/list]

Maybe this isn’t unusual, but it’s definitely a new one for me, and I’m wondering how much all of this is related, or if I have multiple issues.

I filmed a short video showing the behavior: https://youtu.be/a70kyPB2X_k

PS: I realized this place is fairly well abandoned after posting this, but no harm leaving it up.