Star Trek TV shows series - help

I noticed that Star Trek Enterprise was not on the Star Trek DVDs series. So I added it with a different group title. But now it is stuck at the top, and when I try to change the ordering of the groups, that one is locked (!?) and at the top and I can't change it. Help? I also note that there is no "core" here, though maybe that should be the original series.

This series: https://www.librarything.com/nseries/5771/Star-Trek-DVDs

I changed the original series to "core", then I was able to move the enterprise sub-series. Then I put the original series back to "The Original Series" and it is now locked at order 1, which is okay. I guess it gets messed up when there is no "core" section. Sorry I didn't try this before posting, but if anyone else runs into this, maybe it will help them!!! :)