Help.... Bottom bracket problem
 

I got a new frame for a project.
I tried to install the bottom bracket but it became stuck at some point. I had to use a lot of force to remove it...
One she'll has been destroyed but the threads on the frame seems not that bad as I was expecting. Basically I had to remove one turn of the shell's tread from the frame itself.
Now the frame have this Grove and I can't fit manually a new bottom bracket on the left side.
Should I contact the seller? Was the bottom bracket faulty? Ovalized or uncleaned to cause this?
Should I install a new cup forcing in? Or should I make a tread cutter from an old cut?
I don't know if that was my fault, honestly I assembled lots of bikes and I can't understand what I done wrong...
I'm in fear in case I've done some huge damage.
Please check the photos below.

https://i.ibb.co/fbx8HvQ/IMG20251010192602.jpg https://i.ibb.co/TQw8f63/IMG20251010192552.jpg https://i.ibb.co/7N6XFFRt/IMG20251010192557.jpg https://i.ibb.co/PzCH7v3M/IMG20251010192432.jpg

I'm really not sure if it was your fault or not. Now that the damage is done, I'd be inclined to get a bottom bracket tap and clean up the threads with that. There's a local bike co-op here where I've borrowed one; you might be able to find something similar where you are.

Is it a brand new frame? Are you able to verify that it has the correct threading for your bottom bracket?

Yeah its new.
Also the size were correctly. As you can see the start of the tread were working fine and then... Sh*t happens ☠️

How much did you pay for the frame?

You say new frame and new project, so, it seems you have already invested some money into it. If I were you, I would take it to the bike shop and have them chase the threads, and maybe, have them install the bottom bracket too.

The bottom bracket is the heart of the bike. The most important thing. No?

250eur
Internet seller but a real store 😭

Shell out another €50/€75/€100 and let a bike shop near you chase or tap the threads and install the bottom bracket. The rest of the project, I think, you can handle.

A €250 investment becomes a €300/€350 investment. But what should you do?

https://custom-junkies.com/threadles...et-yst-bb-0901

​​​​​​https://www.simplebikestore.eu/produ...Hy-tFP_Iuq40pw

Update. I found another old shell. I installed by hands working slowly with a bit of grease until it reach the end.
Seems stay fit, probably I can add a bit of tread lock too just to be sure that would not move. Honestly did not expect that to fit easy, probably another confirm that I'm an overthinker

This is why we always start threads by hand - if you use a tool everything can feel fine until it isn't, the thread galls and you're left with a mess to clear up. It's a good idea to chase the bottom bracket after galling has occurred, because part of the cup thread may now be welded to the shell, making the cup hard to remove in future.

Conversely, part of the shell may also be welded to the cup. If you intend to reuse the cup, be sure to clean the threads thoroughly with a stiff wire brush and inspect for remaining debris. You may have to dig it out with a pick or even chase the cup threads with a thread file.

UPDATE: turns out the frame was faulty, but the fun fact is that the seller gave up after there is no way to insert the dropout and the thru axle since the rear part is not aligned.
Fun fact x2 the frame was not from china but from an Italian store that sells rough "frames".
at least i'm getting my money back