Ref 14759 SC-61 case identification help

Hi
I’m reaching out for help to resolve this mystery.
Given a Seamaster with this reference I bought some time ago for a project to work on.
The watch was in one piece, no red flags as I could see. After dismantling and cleaning the case I’m no longer able to put the caseback back to the case. I know it sounds weird. I don’t recall removing the caseback was a problem at the first place. But I start to wonder it’s not the caseback for this case. I dealt with a good number of vintage Omega and never experienced such. Already when starting to screw the caseback, it doesn’t feel a good fit. Occasionally I can turn a few time but definitely not enough to close the case. Note the gasket has been removed but even so it’s far from a closed position.
Can someone help me review the case based and determine if I’m dealing with a franken case perhaps? I looked pictures of the same reference but it looks ok.

Thank you in advance!

To me the threads looks damaged in the last picture, all those shiny spots could indicate that the thread tops are bent or worn down. At the left side it looks like the thread splits in two, an indication of cross threading.

My screen is small, but I got new glasses so I am almost certain these threads are damaged. I had the same trouble with a milling machine chuck the other day. Two hours of work with a thread file and a triangular file I fixed it. Do watch makers repair threads and with what kind of tools or do they just swap cases?

Thank you @Dan S and @hen for your prompt responses. Much appreciated!
Yes, it really looks like the threads are damaged.
I took a few macros. It is indeed visible around the stem-hole.
@hen, your question is the main point here. Is that somehow fixable?

Thank you @Dan S ! And thank you for the contact recommendation!

Do watch makers have tools like this, with a finer pitch.

That is true they are not particularly effective on high grade steels, but often its the only alternative for threads M20 and bigger where taps and dies usually aren't available. Most times you need a lot of strong swear words and time in addition to the thread file.