Parsing error from Raiserror

Question

Hi,

Bit of a strange one.

We have a Synapse DW which was running at 200c for R&D yesterday, which showed some strange error behaviour.

We ran the procedures in Synapse from ADF, and the error message passed back to ADF was:
Parse error at line: 3, column: 6: Incorrect syntax near 'NULL'.

Searching the code high and low for anything that could cause a parsing error like this, we found nothing. Absolutely nothing.

So we went deeper. sys.dm_pdw_exec_requests led us to sys.dm_pdw_errors, and this is where we found something pretty strange.

We can see that the DB raised a 8642 exception ("The query processor could not start the necessary thread resources for parallel query execution. Reduce load on the server or use the MAXDOP setting to limit parallelism"), which we would have been perfectly happy to have seen as our error message in ADF.
We can however see an additional 6 errors happening: all in the same session_id, and the original thread_id sharing an error for the parsing.

What we think has happened, is that the internal DMS error, in the process of raising the exception, has somehow resulted in a NULL parsing problem, replacing the original error in the error stack - meaning that ADF never saw the original error.

Is it a bug? How does one raise the bug? We've persisted the information from the error so that we can get back to it - we didn't however persist the information from sys.dm_pdw_exec_requests - so we can't link the request_id to whatever it was that was running.

Any thoughts would be welcome...