Bug. Offset loses reference.

[HughesTooling]

I was trying to fix a model for a customer based on an ellipse with offsets created on a projected face. The problem is if the face is modified before the sketch the offset loses its reference even though I projected the face, not the edge. And because the offset is a spline you end up with something you can't constrain and a broken design. Only option is delete the unconstrained spline and recreate the offset. This of course breaks the next extrude then all the other downstream features.

Here's a simple example, sketch on face, project face then offset projection. Files attached.

Now add a fillet to the edge before the sketch, this breaks the offset and leaves a unconstrained spline that no longer updates and can be moved. Surely the offset could be made to pickup the projected face edge.

Thanks Mark

Edit. Even if i use an edge, after using manage lost projection to reselect the edge it breaks the offset. With the face I can sort of understand it could be difficult to pickup the new edge but if I'm reselecting an edge the offset should not break.

[Phil.E]

This example is a little easier to interpret. The face is projected, but the offset only operates on the prior curves.

Steps taken:

1. Made a box

2. Offset a work plane and projected the box face

3. Offset the box face loop

4. Rolled back timeline and added fillet

5. Rolled timeline to end of model

Result: the fillet created a new edge ID for the projected face. It wasn't consumed by the offset sketch operation.

Expect: The addition of the fillet should provide a new edge ID to the face, and that should carry thru to the projected loop. But it doesn't.

Reported as FUS-123563

[Phil.E]

@HughesTooling Our expectations might be out of line here. It does seem reasonable since the inputs are really straightforward, but I tried it in Inventor and get the same result. 

I'll follow up if I hear why this is a special case for sketch offset.