Improved breakdowns: Remove non-deterministic changes to breakdown_chance.

These cause desyncs in multiplayer.

src/settings.cpp

@@ -1016,6 +1016,14 @@ static bool RoadVehAccelerationModelChanged(int32 p1)
 			}
 		}
 	}
+	if (_settings_game.vehicle.roadveh_acceleration_model == AM_ORIGINAL || !_settings_game.vehicle.improved_breakdowns) {
+		RoadVehicle *rv;
+		FOR_ALL_ROADVEHICLES(rv) {
+			if (rv->IsFrontEngine()) {
+				rv->breakdown_chance = 128;
+			}
+		}
+	}
 
 	/* These windows show acceleration values only when realistic acceleration is on. They must be redrawn after a setting change. */
 	SetWindowClassesDirty(WC_ENGINE_PREVIEW);

src/train_cmd.cpp

@@ -484,8 +484,13 @@ void Train::UpdateAcceleration()
 	assert(weight != 0);
 	this->acceleration = Clamp(power / weight * 4, 1, 255);
 
-	/* for non-realistic acceleration, breakdown chance is 128, corrected by the multiengine factor of 3/(n+2) */
-	this->breakdown_chance = min(128 * 3 / (this->tcache.cached_num_engines + 2), 5);
+	if (_settings_game.vehicle.improved_breakdowns) {
+		if (_settings_game.vehicle.train_acceleration_model == AM_ORIGINAL) {
+			this->breakdown_chance = max(128 * 3 / (this->tcache.cached_num_engines + 2), 5);
+		}
+	} else {
+		this->breakdown_chance = 128;
+	}
 }
 
 /**

src/vehicle.cpp

@@ -116,16 +116,12 @@ void VehicleServiceInDepot(Vehicle *v)
 	v->reliability = e->reliability;
 	v->breakdown_ctr = 0;
 	v->vehstatus &= ~VS_AIRCRAFT_BROKEN;
-	/* Prevent vehicles from breaking down directly after exiting the depot. */
-	v->breakdown_chance /= 4;
 	SetWindowDirty(WC_VEHICLE_DETAILS, v->index); // ensure that last service date and reliability are updated
 
 	do {
 		v->date_of_last_service = _date;
 		v->breakdowns_since_last_service = 0;
 		v->reliability = v->GetEngine()->reliability;
-		/* Prevent vehicles from breaking down directly after exiting the depot. */
-		v->breakdown_chance /= 4;
 		v = v->Next();
 	} while (v != NULL && v->HasEngineType());
 }