Logically i think first thing to look at is therapy itself as a potential primary driver of the feelings, especially if there are repeating patterns.

The whole point of therapy is supposed to be its unique arrangement. But when the client responds in kind to the uniqueness or weirdness of it, the arrangement itself is immediately disregarded and everything is about childhood. It's a sleight of hand, but i dont think therapists are aware of it.

Also in my experience what matters more than identifying the origin of the feelings is what those feelings are doing to you. Seems people are conditioned to overlook extreme distress in therapy on the basis that it's part of some process.