When you insert a CD for the first time, MC analyses it and create a record in its CD Database.
When you RIP a CD MC creates a record in its Main Database.
If you have changed Views, it is possible that your View could be looking in the two databases.
If the CD is showing in Unassigned, that means that the CD doesn't have a value assigned to the attribute that you are primarily sorting on. For example, if your CD doesn't have anything in the [Artist] field, and you look in the Artist View, the CD will show up in the Unassigned category. Same if there is no value in the [Genre] field, and you look at the Genre View, the CD will show up in the Unassigned category.
When you RIP a CD, if you have an internet connection, MC will try to look up the CD and gather metadata about it, and therefore should have values in most common fields, such as [Artist] and [Genre]. But if the CD isn't common, there may not be any data available to download, so the fields may remain empty, hence Unassigned in some Views.
MC doesn't put two copies in the Library when you RIP a CD. You shouldn't see the CD twice in one View, once identified correctly, and once in Unassigned. But you can see it identified correctly in one View, and identified as Unassigned in another View.
So, please try to describe in some more detail what you are actually seeing.
What exact version of MC are you using? i.e. MC24.0.68?
Are you seeing this is Standard View or Theatre View?
What Views are you using? Artist? Album? Genre? Files? A custom View you made?
Do both "copies" of the CD point to the exact same location on your hard drive, NAS, or other storage device?
Are you able to post an image of where you see Unassigned?
Over to you.