Weaving fails with NullReference


I tested SheepAspect, and it worked fine. Now I wanted to port it into my new Application. I installed the NuGET, added my Aspect with the corresponding Cutpoints and compiled. NullReference Exception. If I use SAQL for my pointcut which would result in it being applied nowhere, the build and the weaving works (noticed this when I had a typo in my namespace.
Is there a way to debug the weaving so I can try to figure out where thisNullReference comes from?