I was getting that error also yesterday. Started happening yesterday when I updated a KB with only minor changes. I searched here and didn't see any answers. I tried re-creating the KB, re-creating as a text-only KB (instead of document), creating a separate workflow to isolate that KB, rewriting the query in different ways....found no way around it. My guess is that something has changed with the vector DB creation, because my older bot is still working with a nearly identical KB document. I ended up just hardcoding the data for that node 😦