Thank you for posting query in Microsoft Q&A error.
This error will usually occurs when we are referencing to some null as object.
Could you please check all your datasets and linked services are pointing to data and resources correctly?
More details on implementations steps along with screenshots, Source and Sink configuration details may helpful to understand issue better.
Internally, When I checked this strange error also happen if there is any "Outage in Central US due to unhealthy node". Support engineers can mitigate if that is the case.
You can consider having support ticket for this issue if you don't see no flaws in your implementation and no where you are referring nulls.
Below link helps with creating support ticket.
Hope this will help. Please let us know if any further queries.
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