Failed to create Livy session for executing notebook

We on occasion get the below error
Exception: Failed to create Livy session for executing notebook. LivySessionId: 17602, Notebook: nbPassthrough.\n--> Spark_User_AutoClassification_attempt_Diagnostics: Livy session has failed. Session state: Dead. Error code: Spark_User_AutoClassification_attempt_Diagnostics
A re-run goes through successfully so not a code or data issue. None of our files being processed are large so should not be a data size issue, and failing shortly after starting is just as frequent as anything longer running (although generally none of them run longer than 10-15 minutes).
There can be a number of notebooks running at once - are there shared resources among the notebooks? Or should each have it's own guaranteed set of nodes with their own resources (certainly how I've read the configuration)?
Any ideas how we can go about figuring out what is causing the failures?