Wasn't able to reproduce the issue on DSS 9.0.3
Can you please confirm
1) If project libraries and notebooks are in the same project
2) If you are running the notebook kernel locally, or is it containerized?
If there are we may need to have a closer look at your environment so I would suggest you raise a support ticket along with the instance diagnostics.
I was able to reproduce the same error if I point to inexisting file but I get slightly different error. The search path also includes the project in my case :