It's happened a few times now with both my T's , and they've engaged with me to see what it is as they both say whatever is happening is two people contributing to it ( good T's do this ). It's anger on the surface , underneath is hurt , sadness , exasperation and all sorts of feelings and transference from different people. I feel like leaving therapy when it happens , but I've ploughed on and it's been healing , although it's painful.