Trying to get "oft-interleave-layers" plug-in to work.

[rich2005]

Without your Gimp .xcf file with paths, only a guess maybe some left over control points from a selection to path.

It is possible to make a two control point ellipse using the paths tool, just takes a little care over direction of the path and how to edit it.

   

A four minute video that might help.  https://youtu.be/0wskpFWy6uk