S Haster thanks for more logging info. The PR still looks like it could help.

As for upgrading...
The proper way would be to update WFLY to Weld 3.0.4.Final which was released in the meantime (using the patch and the how-to described in the end of the release article) and then upgrade core to 3.0.5 snapshot.

If you just bump core from 3.0.3.Final to 3.0.5-SNAPSHOT, I think it won't work (there was an API update so core will expect to use a version of API which won't exist).