diff --git a/McZapkie/MOVER.h b/McZapkie/MOVER.h
index 825bec6d..6a70147a 100644
--- a/McZapkie/MOVER.h
+++ b/McZapkie/MOVER.h
@@ -1943,7 +1943,7 @@ class TMoverParameters
 	double MirrorVelClose{5.0};
 	bool MirrorForbidden{false}; /*czy jest pozwolenie na otworzenie lusterek (przycisk)*/
 	bool ScndS = false; /*Czy jest bocznikowanie na szeregowej*/
-	bool ScndCtrlResistiveLock{false}; // the shunt controller can't be moved up while the master controller is at zero or on a resistive position (ScndCtrlResistiveLock=Yes in Cntrl.)
+	bool ScndCtrlResistiveLock{false}; // the shunt controller can't be moved, up or down, while the master controller is at zero or on a resistive position, and drops to 0 when the master controller gets there (ScndCtrlResistiveLock=Yes in Cntrl.)
 	bool SpeedCtrl = false; /*czy jest tempomat*/
 	speed_control SpeedCtrlUnit; /*parametry tempomatu*/
 	double SpeedCtrlButtons[10]{30, 40, 50, 60, 70, 80, 90, 100, 110, 120}; /*przyciski prędkości*/
@@ -2373,8 +2373,11 @@ class TMoverParameters
 	bool IncScndCtrl(int CtrlSpeed);
 	bool DecScndCtrl(int CtrlSpeed);
 	int GetVirtualScndPos() const;
-	// whether ScndCtrlResistiveLock keeps the shunt controller from being moved up at the current master controller position
+	// whether ScndCtrlResistiveLock keeps the shunt controller from being moved at the current master controller position
 	bool IsScndCtrlLockedByMainCtrl() const;
+	// ScndCtrlResistiveLock: the shunt controller drops to 0 once the master controller is at zero or on a resistive position, so it
+	// can't stay engaged there, locked in place (eu07/maszyna#402)
+	void ScndCtrlResistiveLockCheck();
 	bool IsScndCtrlNoPowerPos() const;
 	bool IsScndCtrlMaxPowerPos() const;
 
diff --git a/McZapkie/Mover.cpp b/McZapkie/Mover.cpp
index b9d18d0b..8154eb92 100644
--- a/McZapkie/Mover.cpp
+++ b/McZapkie/Mover.cpp
@@ -1631,6 +1631,8 @@ void TMoverParameters::compute_movement_(double const Deltatime)
 			BRVentilators = false;
 	}
 
+	// the master controller set directly, not through IncMainCtrl()/DecMainCtrl() (AI, consist): the locked shunt follows it as well
+	ScndCtrlResistiveLockCheck();
 	// automatyczny rozruch
 	if (EngineType == TEngineType::ElectricSeriesMotor && AutoRelayCheck())
 	{
@@ -2537,6 +2539,7 @@ bool TMoverParameters::IncMainCtrl(int CtrlSpeed)
 
 	if (true == OK)
 	{
+		ScndCtrlResistiveLockCheck(); // e.g. from the last series position on to the resistive parallel ones
 		SendCtrlToNext("MainCtrl", MainCtrlPos, CabActive); //???
 		SendCtrlToNext("ScndCtrl", ScndCtrlPos, CabActive);
 	}
@@ -2662,6 +2665,7 @@ bool TMoverParameters::DecMainCtrl(int CtrlSpeed)
 
 		if (OK)
 		{
+			ScndCtrlResistiveLockCheck(); // the shunt drops when the master controller leaves a resistance-free position
 			/*OK:=*/SendCtrlToNext("MainCtrl", MainCtrlPos, CabActive); // hmmmm...???!!!
 			/*OK:=*/SendCtrlToNext("ScndCtrl", ScndCtrlPos, CabActive);
 		}
@@ -2822,7 +2826,7 @@ bool TMoverParameters::DecScndCtrl(int CtrlSpeed)
 	}
 	else if (ScndCtrlPosNo > 0 && CabActive != 0)
 	{
-		if (ScndCtrlPos > 0 && !CoupledCtrl && (EngineType != TEngineType::DieselElectric || !AutoRelayFlag))
+		if (ScndCtrlPos > 0 && !CoupledCtrl && (EngineType != TEngineType::DieselElectric || !AutoRelayFlag) && !IsScndCtrlLockedByMainCtrl())
 		{
 			if (CtrlSpeed == 1)
 			{
@@ -2878,6 +2882,16 @@ bool TMoverParameters::IsScndCtrlLockedByMainCtrl() const
 	return ScndCtrlResistiveLock && (IsMainCtrlNoPowerPos() || RList[MainCtrlPos].R >= 0.01);
 }
 
+void TMoverParameters::ScndCtrlResistiveLockCheck()
+{
+	// the shunt controller, locked in both directions on zero and the resistive positions, would otherwise stay engaged there once the
+	// master controller is taken back (or set from elsewhere, e.g. by the AI or another vehicle of the consist) with the shunt on
+	if (ScndCtrlPos > 0 && !CoupledCtrl && IsScndCtrlLockedByMainCtrl())
+	{
+		ScndCtrlPos = 0;
+	}
+}
+
 int TMoverParameters::GetVirtualScndPos() const
 {
 	if (TrainType == dt_ET42 && DynamicBrakeFlag && !ScndCtrlPos)
diff --git a/tests/unit/test_cntrl.cpp b/tests/unit/test_cntrl.cpp
index e6c53940..c73c45d8 100644
--- a/tests/unit/test_cntrl.cpp
+++ b/tests/unit/test_cntrl.cpp
@@ -96,12 +96,71 @@ TEST_CASE("cntrl: ScndCtrlResistiveLock keeps the field shunting off at zero and
 				CHECK(locked->ScndCtrlPos == 1);
 			}
 		}
-		SUBCASE("the shunting still goes off on a resistive position") {
+		SUBCASE("the shunt goes down on a resistance-free position") {
+			controllers_at(locked, resistancefree);
+			REQUIRE(locked->IncScndCtrl(1));
+			REQUIRE(locked->IncScndCtrl(1));
+			CHECK(locked->DecScndCtrl(1));
+			CHECK(locked->ScndCtrlPos == 1);
+			CHECK(locked->DecScndCtrl(2));
+			CHECK(locked->ScndCtrlPos == 0);
+		}
+		SUBCASE("the shunt doesn't go down on a resistive position either") {
+			// a state the lock doesn't let arise (see below), set by hand to check the controller alone
+			controllers_at(locked, resistancefree - 1);
+			locked->ScndCtrlPos = 1;
+			CHECK(locked->IsScndCtrlLockedByMainCtrl());
+			CHECK_FALSE(locked->DecScndCtrl(1));
+			CHECK_FALSE(locked->DecScndCtrl(2));
+			CHECK(locked->ScndCtrlPos == 1);
+		}
+		SUBCASE("the master controller taken back from a shunt step drops the shunt") {
+			controllers_at(locked, resistancefree);
+			REQUIRE(locked->IncScndCtrl(1));
+			if (locked->TrainType == dt_ET22) {
+				// the ET22's master controller doesn't turn with the shunt on: the shunt goes off first, as before
+				CHECK_FALSE(locked->DecMainCtrl(1));
+				CHECK(locked->MainCtrlPos == resistancefree);
+				CHECK(locked->DecScndCtrl(1));
+			}
+			CHECK(locked->DecMainCtrl(1));
+			CHECK(locked->MainCtrlPos == resistancefree - 1);
+			CHECK(locked->ScndCtrlPos == 0);
+			// and the master controller goes on down to zero, nothing left locked
+			while (locked->MainCtrlPos > 0 && locked->DecMainCtrl(1)) {
+			}
+			CHECK(locked->MainCtrlPos == 0);
+		}
+		SUBCASE("the master controller set directly (AI, consist) drops the shunt in the next update") {
 			controllers_at(locked, resistancefree);
 			REQUIRE(locked->IncScndCtrl(1));
 			locked->MainCtrlPos = resistancefree - 1;
-			CHECK(locked->DecScndCtrl(1));
+			locked.step();
 			CHECK(locked->ScndCtrlPos == 0);
+			CHECK(locked->MainCtrlPos == resistancefree - 1);
+		}
+		SUBCASE("the master controller moved up from a shunt step onto a resistive position drops the shunt") {
+			// the last series position, followed by the resistive parallel ones
+			auto lastseries{0};
+			for (auto position{resistancefree}; position > 0 && position < locked->MainCtrlPosNo; position = resistance_free_position(locked.mover(), position)) {
+				if (locked->RList[position + 1].R >= 0.01) {
+					lastseries = position;
+					break;
+				}
+			}
+			REQUIRE(lastseries > 0);
+			controllers_at(locked, lastseries);
+			locked->DirActive = 1;
+			REQUIRE(locked->IncScndCtrl(1));
+			if (locked->TrainType == dt_ET22) {
+				CHECK_FALSE(locked->IncMainCtrl(1)); // the ET22's interlock, as before
+				CHECK(locked->ScndCtrlPos == 1);
+			}
+			else {
+				CHECK(locked->IncMainCtrl(1));
+				CHECK(locked->MainCtrlPos == lastseries + 1);
+				CHECK(locked->ScndCtrlPos == 0);
+			}
 		}
 	}
 }