Thread is get getting info from old file

In my project I am using Assistant API V2 with file search (retrieval) and the knowledge base is stored in file and from this file the vector store is created, then this vector store is used for Assistant.

When I try to update the vector store, I delete the old one and attach the new one to Assistant.

The problem is, when I try to update the knowledge base, the threads created before this update retrieve data from the old one, they are not updated.

Is there a way to update the old threads or should I delete them and create new ones?