Why Can't Some Projects Move to Different Existing Project Sub-Categories?

Hi, GSA friends and peoples of the world.

I was wondering why some projects won't move when I try.

Ordinarily, projects, and their Tiers as well, would move, if I select just the main project?

Or, do I select them all?

Or, is this not possible for a project with Tiers, as I've tried this all...

I don't know what it is. Am I used a certain char or are the names too long?

Trying to move from:

Root>>Sub

to

Root>>Sub>>Sub-Sub

but this one project and its tiers won't move.

This has happened a few times before...

Any help would be greatly appreciated...!