This, basically. I have an acquired brain injury. I've had an argument with my husband's mother. Turns out he had scapegoated me to her (told her in the heat of an argument that I hated her, which I'd never expressed). I suffer from confabulation (false memory) and could explain away every fault in my arguments just by telling her "I'm really sorry I said those things; I suffer from confabulation as a result of a very serious brain injury" (which she knows about). My husband says I can't do it, I am unable to start again because I'm not forgiving enough, and that he and his therapist have agreed that I can never tell an abusive narcissist that my brain fills in gaps in memory with false memories because she'll use it against me/abuse the information and me.
The thing is, my brain injury could explain everything away, we could start from scratch. We could have a positive relationship.