Decision Tree Classifier to classify values based on values of other columns
Couple of things:
Cant replicate the problem exactly but if you follow these steps you are not exposing yourself

TfidfVectorizer is CountVectorizer + TfidfTransformer, you are exposing yourself to unnecessary complexity and potential errors

Use pipelines, cant stress this enough, its a compact way to pack all the sklearn transformers together AND THEN use fit, predict methods...

I would advise you to follow something like that, or find similiar problem here