diff --git a/examples/synthetic_graph_evolution/simple_run.py b/examples/synthetic_graph_evolution/simple_run.py
index fdce35f6..85dad723 100644
--- a/examples/synthetic_graph_evolution/simple_run.py
+++ b/examples/synthetic_graph_evolution/simple_run.py
@@ -30,7 +30,7 @@ def run_graph_search(size=16, timeout=8, visualize=True):
     requirements = GraphRequirements(
         early_stopping_iterations=100,
         timeout=timedelta(minutes=timeout),
-        n_jobs=-1,
+        n_jobs=1,
     )
     gp_params = GPAlgorithmParameters(
         genetic_scheme_type=GeneticSchemeTypesEnum.parameter_free,
diff --git a/golem/core/constants.py b/golem/core/constants.py
index 4104ead3..d0aaa01d 100644
--- a/golem/core/constants.py
+++ b/golem/core/constants.py
@@ -4,6 +4,6 @@
 MAX_TUNING_METRIC_VALUE = np.inf
 MIN_TIME_FOR_TUNING_IN_SEC = 3
 # Max number of evaluations attempts to collect the next pop; See usages.
-EVALUATION_ATTEMPTS_NUMBER = 5
+EVALUATION_ATTEMPTS_NUMBER = 10
 # Min pop size to avoid getting stuck in local maximum during optimization.
 MIN_POP_SIZE = 5
diff --git a/golem/core/optimisers/adaptive/operator_agent.py b/golem/core/optimisers/adaptive/operator_agent.py
index 10e0175e..93658d55 100644
--- a/golem/core/optimisers/adaptive/operator_agent.py
+++ b/golem/core/optimisers/adaptive/operator_agent.py
@@ -102,8 +102,12 @@ def _dbg_log(self, obs, actions, rewards):
                 msg += (f'avg={nonzero.mean()} std={nonzero.std()} '
                         f'min={nonzero.min()} max={nonzero.max()} ')
 
+            def get_name(obj):
+                return getattr(obj, '__name__', str(obj))
+
             self._log.info(msg)
-            self._log.info(f'actions/rewards: {list(zip(actions, rr))}')
+            action_strs = map(get_name, actions)
+            self._log.info(f'actions/rewards: {list(zip(action_strs, rr))}')
 
             action_values = list(map(self.get_action_values, obs))
             action_probs = list(map(self.get_action_probs, obs))
diff --git a/golem/core/optimisers/genetic/evaluation.py b/golem/core/optimisers/genetic/evaluation.py
index 3df1a916..a0736c5e 100644
--- a/golem/core/optimisers/genetic/evaluation.py
+++ b/golem/core/optimisers/genetic/evaluation.py
@@ -146,8 +146,8 @@ def population_evaluation_info(self, pop_size: int, evaluated_pop_size: int):
         if pop_size == 0 or evaluated_pop_size / pop_size <= STAGNATION_EVALUATION_PERCENTAGE:
             success_rate = evaluated_pop_size / pop_size if pop_size != 0 else 0
             self.logger.warning(f"{evaluated_pop_size} individuals out of {pop_size} in previous population "
-                                f"were evaluated successfully. {success_rate}% "
-                                f"is a fairly small percentage of successful evaluation.")
+                                f"were evaluated successfully. {success_rate} "
+                                f"is a fairly small fraction of successful evaluation.")
         else:
             self.logger.message(f"{evaluated_pop_size} individuals out of {pop_size} in previous population "
                                 f"were evaluated successfully.")
diff --git a/golem/core/optimisers/genetic/operators/reproduction.py b/golem/core/optimisers/genetic/operators/reproduction.py
index 60de62f3..16e95fa7 100644
--- a/golem/core/optimisers/genetic/operators/reproduction.py
+++ b/golem/core/optimisers/genetic/operators/reproduction.py
@@ -83,6 +83,9 @@ def reproduce_uncontrolled(self,
         new_population = self.crossover(selected_individuals)
         new_population = ensure_wrapped_in_sequence(self.mutation(new_population))
         new_population = evaluator(new_population)
+        # Guard against None errors
+        if new_population is None:
+            new_population = []
         return new_population
 
     def reproduce(self,
diff --git a/golem/core/optimisers/populational_optimizer.py b/golem/core/optimisers/populational_optimizer.py
index 478f2a03..5e27c453 100644
--- a/golem/core/optimisers/populational_optimizer.py
+++ b/golem/core/optimisers/populational_optimizer.py
@@ -46,8 +46,7 @@ def __init__(self,
         self.generations = GenerationKeeper(self.objective, keep_n_best=requirements.keep_n_best)
         self.timer = OptimisationTimer(timeout=self.requirements.timeout)
 
-        dispatcher_type = MultiprocessingDispatcher if self.requirements.parallelization_mode == 'populational' else \
-            SequentialDispatcher
+        dispatcher_type = MultiprocessingDispatcher if self.requirements.n_jobs != 1 else SequentialDispatcher
 
         self.eval_dispatcher = dispatcher_type(adapter=graph_generation_params.adapter,
                                                n_jobs=requirements.n_jobs,
diff --git a/test/unit/optimizers/gp_operators/test_reproduction_controller.py b/test/unit/optimizers/gp_operators/test_reproduction_controller.py
index e1034f45..a7fd660c 100644
--- a/test/unit/optimizers/gp_operators/test_reproduction_controller.py
+++ b/test/unit/optimizers/gp_operators/test_reproduction_controller.py
@@ -83,7 +83,7 @@ def test_mean_success_rate(reproducer: ReproductionController, success_rate: flo
     assert np.isclose(reproducer.mean_success_rate, success_rate, rtol=0.1)
 
 
-@pytest.mark.parametrize('success_rate', [0.0, 0.1])
+@pytest.mark.parametrize('success_rate', [0.0, 0.04])
 def test_too_little_valid_evals(reproducer: ReproductionController, success_rate: float):
     evaluator = MockEvaluator(success_rate)
     pop = get_rand_population(reproducer.parameters.pop_size)
@@ -92,7 +92,7 @@ def test_too_little_valid_evals(reproducer: ReproductionController, success_rate
         reproducer.reproduce(pop, evaluator)
 
 
-@pytest.mark.parametrize('success_rate', [0.2])
+@pytest.mark.parametrize('success_rate', [0.15])
 def test_minimal_valid_evals(reproducer: ReproductionController, success_rate: float):
     parameters = reproducer.parameters
     evaluator = MockEvaluator(success_rate)