A specific, core issue arises when we pattern by reference off another patterned copy geom.
the source part contains a pattern of three surfaces.
One of those surfaces is copy geom'd into the target part.
That copy geom is then patterned on the target part.
This creates an issue because there are now two links to the target part.
The geometry is linked to the part via a Copy Geometry.
The pattern count itself is linked to the part via the pattern.
This means that we can break updates to the geometry by setting the Copy Geom to Manual Update.
However the pattern count/positioning is now unbreakable, it is always live. Setting the Copy Geom to Manual Update has no effect on the pattern count/position, it is not in control of that, the pattern is.
This means that if a company has protocols forcing Manual Update on release (e.g. ModelCHECK external reference checks), these parts will never pass, because that pattern link is always live. This also creates the obvious problem of the pattern count/position updating if the item is opened in the future (although the geometry will not, which makes things even more wrong).
The pattern itself should have an Automatic/Manual update toggle, to provide a path to resolve this situation.