Sounds like a crank or roller plate went and damaged the case.
Unfortunately this is a regular occurrence.
Have a look inside with a torch and see if you can see the evidence of it inside the crankchamber.
Years ago I broke quite few cranks, but then I was racing and pushing it hard
I used to fill up the cases with body filler to keep it running, but it worked.
Our current racing case has a small hole where we lost a screw and the rod punched it through. We plugged it with Super epoxy and bandage in the paddock and I believe we only missed one race. It is still there. If the repair has been made with filler and it works, just accept it. Those who want it back to metal standard must have a deep pocket as before the case is heated to weld properly, you must remove the cups by destroying the shrink rings first and warming the case. Then weld, which distorts the case, then re machine to get back alignment accuracy, then fit oversize cups and fit new shrink rings.
For what? If it goes and the repair is not offensive to the eye, just live with it. The main thing is to have it in a state where you can ride it.
It will not go any better if you do all the work I mention.
Life is not perfect, try to live with it
And never let me hear you talk about giving up again.
Many people are taking a big interest in your efforts and try to give advice where possible. Dont let them or more important, yourself down.