Hey there!
We recently released v9.0.
In that version, we are ignoring user-supplied sonar.sources and sonar.tests.
Based on how the scanner for .NET works, there is no reason to use these parameters.
In fact, if you used them before v8.0, it was at best a no-op and at worst a double-index failure.
After v8.0, it resulted almost always to a double index error.
After v9.0, the bug was fixed and the program should no longer crash.
In any case, to simplify your pipeline I would suggest not including these parameters to your begin step.
Cheers, thanks for the report!
It was quite helpful 