anchor.diff:      #trace_state{enabled = Enabled, sleep_set = SleepSet,
                    error_nxt = ErrorNext, last = {Lid, _, _},
                    preemptions = Preemptions} = TraceTop,
  -    ?debug("Pick next: Enabled: ~w Sleeping: ~w\n", [Enabled, SleepSet]),
  +    ?debug("Pick next: Enabled: ~p Sleeping: ~p\n", [Enabled, SleepSet]),
       Choice =
           case ErrorNext of
               none ->
  
positive.code:                                 true  -> ordsets:add_element(Lid, Possible);
                                  false -> Possible
                              end,
                          ?debug("  Backtrack: ~w\n", [Backtrack]),
                          ?debug("  Predecess: ~w\n", [Predecessors]),
                          ?debug("  SleepSet : ~w\n", [SleepSet]),
                          ?debug("  Initial  : ~w\n", [Initial]),
                          case concuerror_lid:deep_intersect_with_fix(Backtrack,
                                                                      Initial) of
                              {true, NewBacktrack} ->
  
negative.code:             NewBacktrack =
                  case Predecessors =:= [] of
                      false ->
                          ?debug(" Add as 'choose-one': ~p\n", [Predecessors]),
                          concuerror_lid:insert_to_deep_list(Backtrack,
                                                             Predecessors);
                      true ->
                          ?debug(" Add as 'choose every': ~p\n", [Candidates]),
                          Fold =
                              fun(E, AccBacktrack) ->
                                      case concuerror_lid:deep_intersect_with_fix(
  