Unexpected surface created when using Extrude Cut tool - With Video

[engineeringNCMXB]

This has me stumped. When trying to cut a feature into my model, a surface is created that covers geometry that it should not cut. I have tried this a number of different ways, including starting from scratch. Any ideas why this is happening? User error? Software bug?

Grateful for any guidance.

 

[TrippyLighting]

Can you share the model?

[engineeringNCMXB]

Sure - let me de-feature it a bit and I will share. Standby.......

[engineeringNCMXB]

In the process of making a de-featured copy.....I discovered something that helps. It feels like I am working around a bug on this one. Strange.....

I moved the sketch plane up, then extruded to the top surface and used an offset to get the cut. It works, but I have no idea why. If I cut directly to the depth, I get the unexpected surface.

 

[jeff_strater]

one of two things is possible here:

1. this is a graphics/faceting glitch, in which case the geometry is fine, but the display just has a few extra triangles
2. there is a sketch visible, and what you are seeing is that sketch

my money is on #1, but we can't tell without the model.