Please see context here: dotnet/arcade#4304 (comment)
From @mikem8361 :
The NullReferenceException definitely needs to be fixed but I'm sure it is either network time out or error path. I can make some simple fixes to log all inner exceptions in the aggregated one to diagnose this in the future.
Example builds:
https://dnceng.visualstudio.com/internal/_build/results?buildId=419023
https://dnceng.visualstudio.com/internal/_build/results?buildId=417308