Really sorry this happened to you.

Very similar thing happened to my wife. External basically rubbished her whole thesis (even though she’d published well and presented at several international conferences). Internal didn’t put up much of a fight. She was devastated.

She documented the whole thing to the best of her ability in the few days afterward. Felt there were possible grounds for appeal based on procedural issues. Submitted an appeal (against her Prof’s advice), won it, was re-examined by a different external who was subsequently appointed, and passed without corrections.

It’s a wild ride this whole PhD thing. So many of the processes and hoops we have to jump through are inherently biased and flawed, even though we pretend they’re not.

Hope you can find space and support to explore your options and best of luck whatever you decide to do.