Derived configuration disappears

Hello;

      This seems a bit strange, as I don't recall running into it. As I'm in a part configuration I create a derived configuration from the configuration & that's fine, but then as I create an additional derived configuration from that  configuration (3rd chain etc.), the component disappears. So

1. I've believe I've done triple configs before, without this happening.

2. I do nothing to the configuration except create it.

     Has anyone run into this type of behavior?

Thanks in advance for any input.

Rob_D SW 2018_sp5.

SolidworksGeneral