Are you using the latest Reactor version? Some posts suggest that a newer version fixes this problem. Also please try deleting the .pdb files of your app before using Reactor, as suggested in the above link, does it work this way?
The x# compiler shares the same backend with a very recent version of the c# compiler (Roslyn), which emits much more sophisticated code/pdb information than vulcan does. It looks like Reactor cannot (yet?) properly "understand" some of this symbol information.