[BUG?] Blueprint containing Casting crashes on compiling

I am attempting to recreate Hit Reaction from Example Content and experiencing a possible bug (4.8 released).

As soon as my tracer (PlayerPawn) casts to its target (Bot), I’ll never be able to compile the Bot again. The only way around is to compile the PlayerPawn and it will compile the Bot as well. Note that both actors are inherited from a custom C++ class.