ISBN connects to wrong work?

I'm trying to add my copies of LOTR but some of the ISBNs I have are linking to the work for The Hobbit instead. I can't quite figure out how to change this.

The Fellowship of the Ring: ISBN 9780008264062 - this one worked properly; the other two did not.
The Two Towers: ISBN 9780008264079
The Return of the King: ISBN 9780008264222

These are from the box set ISBN 9780008260187, which did come with The Hobbit as well.

Apologies in advance if this is the wrong place to ask about this.

From a boxed set chances are that someone entered the wrong title or edited it and left the ISBN. Have you already separated and recombined your editions?

No I haven't - I couldn't find the isbn for my edition on the 'editions' page to separate it. I also haven't done it before so maybe I'm looking for the wrong thing.

Fixed Two Towers.

What you have to do is find the title that does not fit, probably among the 1copy editions. I just found another Two Towers, but my eyes haven't caught Return of the King.

I have to say that The Hobbit is surprisingly clean.

OK So just browse the titles looking for mismatches and hope it's the right one? I'll try that later. Thanks!

Oh I've figured it out; thanks MarthaJeanne. I found the correct isbn-10 equivalent for the copy I had and was able to separate/combine editions properly.

OK, found Return of the King as well. Separated, recombined.

On an easier work I might have tried to show you how to do it yourself, but searching through the editions page of The Hobbit is just plain brutal.

Yeah combing through thousands of editions is a bit much. Thanks again!

The place to ask for help on things like this is https://www.librarything.com/groups/combiners

For combining, it's best to give the book URL. For most other purposes Touchstones are the easiest way to link.