M7 WIP Brep.Split bugs

I have a C# Grasshopper component that has code that splits one brep with four others.

The code is:

Brep[] splitters = new Brep[] { outrWndTrim, outrMidTrim, innrMidTrim, innrWndTrim };
Brep[] surfs = uppr.Split(splitters, t);

In Rhino 6 the surfs array has 5 breps in it.

In Work In Progress (7.0.20238.17095, 8/25/2020) the C# component Split call returns 6 breps and surfs[0] is null.

I tried to create a grasshopper file with a C# script node to illustrate the problem. It has a third, different, behavior. I assigned surfs to A and got three values (null, trimmed surface, trimmed surface)

What’s going on?!?

I have included the Grasshopper file.

m7brepsplitbug.gh (603.5 KB)