[Carver Koella]

For anyone finding this now, I found better luck doing what I wanted by ring selecting the edges and then using the Connect command found in the structure tab (or you can just right-click, of course).
(v 11.5, here)

[Carver Koella]

For anyone finding this later:

I was having a similar issue with MoGraph randomly wigging out, not doing what it was supposed to, rendering nonsense that didn’t happen in the software, etc. I was keyframing Cloner and Text objects with Rigid Body tags set to Follow Position and Rotation (in the Force window of the tag).
Sometimes everything would be fine, sometimes not. I was about to stab an innocent co-worker in frustration. Finally I just (for no sensible reason) disabled Rigid Body and key-framed it to enable 12 or so frames before the object’s first animation, and whaddya know? Works every time. ::shrug::