I have this issue with multiple, unrelated assemblies. Sometimes when I am modelling a part (Part A) in context within an assembly, I will need to make a slightly different version. To do this, I typically have the assembly open, then I open A and save it as a copy (B.) I then close Part A. Going back into the assembly, I click Insert>Component>Existing Part /Assembly. With B already open, it auto populates B into the feature manager. While being sure that my cursor does not go into the graphics area at all, I click on B in the feature manager. B is then displayed in the graphics area in the correct position, lined up perfectly with A. I then click the green check mark in the feature manager (again, the cursor stays out of the graphics pane the entire time.) As soon as I click the check mark, the part disappears from the graphics pane and is placed way off-screen in the middle of nowhere. The baffling thing is that it happens intermittently, and with the exact same cursor movements.
So now, for all the different versions of the same part in my feature tree, some are fixed (with an (f) in front) since they placed in the correct place automatically, and others I had to mate the standard planes manually, so they don’t have the (f).
I guess it’s not a huge deal, but it bothers me that it works sometimes but not others. Am I doing something wrong when placing these new parts? Is there a better approach that I should take when creating similar parts?