Thank you Karsten.

Using Compare plugin in Notepad++ shows that you made changes to vector.js.

After copying the new vector.js to the extension directory, the trochoid and trochoid2 scripts still cannot have their vectors deleted :-(

So there is an objectlist in the geometry database, which MoI cannot delete. (?)
Its objects can be lofted and extended, and such changes can be deleted, but not the original vectors.

- Brian