I’ve got a 14’ sphere that I’ve divided into 18 equal panels, no problem there.
When I next go to split the individual panels using a circle that runs along the equator of the panels, for some reason it gives me 3 surfaces.
If I split the panels using a plane running through the equator it splits into 2 surfaces as expected.
Here’s a closer view of the errant circle split:
I’ve split a lot of things with other things over the years and never encountered this behavior.