Your set up looks okay to me. By simply specifying you encountered a Nil-Nil error, you have robbed the message of all its context. It would be good to show it so we can determine ...

1. What is printing the message? Is it ADE, Spectre, or something else.
2. If it is Spectre printing the message, is it PSS, PAC or something else?

Printing Nil-Nil to identify an error makes it sounds like an internal error produced by ADE, which suggests that maybe you did not set something you should have. You might want look around. If you cannot find anything, you might want to talk to Cadence. Unless this is known problem with a known workaround, it is hard for other users to help you with an internal error.

-Ken