We just updated to NextJS v15 and React v19.

Now we are getting this warning [WebServer] <w> [webpack.cache.PackFileCacheStrategy] Serializing big strings (242kiB) impacts deserialization performance (consider using Buffer instead and decode when needed)

It's causing timeouts affecting our tests.
I have seen this problem reported but we aren't using any of the packages they mention were causing the issue. How would one go about trying to figure out what is causing it?

Thanks