@liliankasem recently fixed #9484 Which has same stack trace. We need to check logs to confirm customer is using a host version with this fix.

@liliankasem recently fixed #9484 Which has same stack trace. We need to check logs to confirm customer is using a host version with this fix.

Running the below query in production shows the issue is happening across versions, including the latest host version. The PR you reference seems to make changes way upstream. I think we need to fix this actual method to prevent errors in any callstacks. E.g. it should do proper null checks and return an empty collection if needed.

All("FunctionsLogs")
| where PreciseTimeStamp > ago(1d)
| where Level == 2
| where Details startswith "System.NullReferenceException : Object reference not set to an instance of an object."
| where Details contains "GetFallbackWorkerConfig()"
| summarize count() by HostVersion
| order by count_ desc
| take 10

The issue primarily stems from the change made in this PR. #9264. The goal of the change in #9264 was to load the latest worker.config when LoadFunctionMetadata() in FunctionMetadataManager. This would allow the customers to use language worker arguments. Prior to this change customers were not able to pass language worker arguments in consumption. The worker config was statically loaded in placeholder and was carried through to the function apps.

Unfortunately, as a result when the LoadFunctionMetadata() is called when the Script host is not available, we run into null ref exception. To resolve this, we would have to examine each scenario where LoadFunctionMetadata() and identify a proper resolution to each one of them.