In the file below, without selecting anything, run MeshIntersect, leave the settings at default. Then type IP to get an infinite plane, choose CPlaneXY as the option and then choose the mesh box.
The mesh intersection fails, but the IP display remains on screen.
MeshIntersectPlane2.3dm (314.3 KB)
Yeah, I think Giulio has the IP drawing one… I’ll see if I can find the YT. Anyway, I see the intersection failure (sometimes) here as well.
So, this is what we have - https://mcneel.myjetbrains.com/youtrack/issue/RH-54886
When the intersect fails, IP hangs around…
Now, I cannot make your example fail.
-Pascal