Here is a short video about the behavior:
https://vimeo.com/348236617
I didn't use any part-design features here but it should show the same problem:
As the number of faces of the gear changes, also the naming of these faces changes and at one point the face which is referenced by the sketch jumps to a different position.
The reason why the sketch is not jumping at first is answered by the observation made with @realthunder's FreeCAD version:
Code: Select all
No planar Face in AttachEngine3D::calculateAttachedPlacement()!
This means after changing the number of tenths a non planar face (most likely a part of the involute) is referenced and an error is reported for LinkStage3-branch. Master simple use the previou location of the sketch.
So we have here an example of the topo-naming issue. Maybe @realthunder can give some better explanation what is going on here.
Also I am still wondering what is different in the version @chrsib made. The posted file seems to work with all different property values.