diff --git a/src/simulation/Simulation.cpp b/src/simulation/Simulation.cpp
index 0780bea4c..d8b19bc37 100644
--- a/src/simulation/Simulation.cpp
+++ b/src/simulation/Simulation.cpp
@@ -1996,11 +1996,8 @@ void Simulation::clear_sim(void)
 	SetEdgeMode(edgeMode);
 }
 
-bool Simulation::IsObsticle(int x, int y, int type)
+bool Simulation::IsWallBlocking(int x, int y, int type)
 {
-	if (pmap[y][x])// && (type != PT_SPRK || !(elements[pmap[y][x]&0xFF].Properties & PROP_CONDUCTS)))
-		return true;
-
 	if (bmap[y/CELL][x/CELL])
 	{
 		int wall = bmap[y/CELL][x/CELL];
diff --git a/src/simulation/Simulation.h b/src/simulation/Simulation.h
index fd65f8252..abcea157f 100644
--- a/src/simulation/Simulation.h
+++ b/src/simulation/Simulation.h
@@ -138,7 +138,7 @@ public:
 	TPT_NO_INLINE int try_move(int i, int x, int y, int nx, int ny);
 	TPT_NO_INLINE int eval_move(int pt, int nx, int ny, unsigned *rr);
 	void init_can_move();
-	bool IsObsticle(int x, int y, int type);
+	bool IsWallBlocking(int x, int y, int type);
 	void create_cherenkov_photon(int pp);
 	void create_gain_photon(int pp);
 	TPT_NO_INLINE void kill_part(int i);
diff --git a/src/simulation/elements/CRAY.cpp b/src/simulation/elements/CRAY.cpp
index 525ba2f06..112dd498c 100644
--- a/src/simulation/elements/CRAY.cpp
+++ b/src/simulation/elements/CRAY.cpp
@@ -87,7 +87,7 @@ int Element_CRAY::update(UPDATE_FUNC_ARGS)
 								break;
 							}
 							r = pmap[y+nyi+nyy][x+nxi+nxx];
-							if (!sim->IsObsticle(x+nxi+nxx, y+nyi+nyy, parts[i].ctype) || (parts[i].ctype == PT_SPRK && sim->elements[r&0xFF].Properties & PROP_CONDUCTS) && !destroy) { // create, also set color if it has passed through FILT
+							if (!sim->IsWallBlocking(x+nxi+nxx, y+nyi+nyy, parts[i].ctype) && (!sim->pmap[y+nyi+nyy][x+nxi+nxx] || (parts[i].ctype == PT_SPRK && !destroy))) { // create, also set color if it has passed through FILT
 								int nr;
 								if (parts[i].ctype == PT_LIFE)
 									nr = sim->create_part(-1, x+nxi+nxx, y+nyi+nyy, parts[i].ctype|(parts[i].tmp2<<8));
diff --git a/src/simulation/elements/PSTN.cpp b/src/simulation/elements/PSTN.cpp
index 7d075a47b..6496483a4 100644
--- a/src/simulation/elements/PSTN.cpp
+++ b/src/simulation/elements/PSTN.cpp
@@ -160,6 +160,37 @@ int Element_PSTN::update(UPDATE_FUNC_ARGS)
 	return 0;
 }
 
+//#TPT-Directive ElementHeader Element_PSTN static int CanMoveStack(Simulation * sim, int stackX, int stackY, int directionX, int directionY, int size, int amount)
+int Element_PSTN::CanMoveStack(Simulation * sim, int stackX, int stackY, int directionX, int directionY, int size, int amount)
+{
+	int posX, posY, r, spaces = 0, currentPos = 0;
+	if (amount == 0)
+		return 0;
+	for(posX = stackX, posY = stackY; currentPos < size + amount; posX += directionX, posY += directionY) {
+		if (!(posX < XRES && posY < YRES && posX >= 0 && posY >= 0)) {
+			break;
+		}
+		r = sim->pmap[posY][posX];
+		if (sim->IsWallBlocking(posX, posY, 0)/* || (r&0xFF) == PT_INSL*/)
+			break;
+		if(!r) {
+			spaces++;
+			tempParts[currentPos++] = -1;
+			if(spaces >= amount)
+				break;
+		} else {
+			if(currentPos < size)
+				tempParts[currentPos++] = r>>8;
+			else
+				return spaces;
+		}
+	}
+	if (spaces)
+		return currentPos;
+	else
+		return 0;
+}
+
 //#TPT-Directive ElementHeader Element_PSTN static int MoveStack(Simulation * sim, int stackX, int stackY, int directionX, int directionY, int size, int amount, bool retract, int callDepth = 0)
 int Element_PSTN::MoveStack(Simulation * sim, int stackX, int stackY, int directionX, int directionY, int size, int amount, bool retract, int callDepth)
 {
@@ -167,8 +198,32 @@ int Element_PSTN::MoveStack(Simulation * sim, int stackX, int stackY, int direct
 	int posX, posY, r, spaces = 0, currentPos = 0;
 	r = sim->pmap[stackY][stackX];
 	if(!callDepth && (r&0xFF) == PT_FRME) {
-		int biggestMove = amount;
+		int ret = amount;
 		int newY = !!directionX, newX = !!directionY;
+		if (!retract)
+		{
+			//check if we can push all the FRME
+			for(int c = 0; c < MAX_FRAME; c++) {
+				posY = stackY + (c*newY);
+				posX = stackX + (c*newX);
+				if (posX < XRES && posY < YRES && posX >= 0 && posY >= 0 && (sim->pmap[posY][posX]&0xFF) == PT_FRME) {
+					int val = CanMoveStack(sim, posX+directionX, posY+directionY, directionX, directionY, size, amount);
+					if(val < amount)
+						amount = val;
+				} else
+					break;
+			}
+			for(int c = 1; c < MAX_FRAME; c++) {
+				posY = stackY - (c*newY);
+				posX = stackX - (c*newX);
+				if (posX < XRES && posY < YRES && posX >= 0 && posY >= 0 && (sim->pmap[posY][posX]&0xFF) == PT_FRME) {
+					int val = CanMoveStack(sim, posX+directionX, posY+directionY, directionX, directionY, size, amount);
+					if(val < amount)
+						amount = val;
+				} else
+					break;
+			}
+		}
 		//If the piston is pushing frame, iterate out from the centre to the edge and push everything resting on frame
 		for(int c = 0; c < MAX_FRAME; c++) {
 			posY = stackY + (c*newY);
@@ -177,9 +232,9 @@ int Element_PSTN::MoveStack(Simulation * sim, int stackX, int stackY, int direct
 				r = sim->pmap[posY][posX];
 				if((r&0xFF) == PT_FRME) {
 					int val = MoveStack(sim, posX, posY, directionX, directionY, size, amount, retract, 1);
-					if(val < biggestMove)
-						biggestMove = val;
-				} else 
+					if(c == 0)
+						ret = val;
+				} else
 					break;
 			}
 		} 
@@ -189,14 +244,12 @@ int Element_PSTN::MoveStack(Simulation * sim, int stackX, int stackY, int direct
 			if (posX < XRES && posY < YRES && posX >= 0 && posY >= 0) {
 				r = sim->pmap[posY][posX];
 				if((r&0xFF) == PT_FRME) {
-					int val = MoveStack(sim, posX, posY, directionX, directionY, size, amount, retract, 1);
-					if(val < biggestMove)
-						biggestMove = val;
-				} else 	
+					MoveStack(sim, posX, posY, directionX, directionY, size, amount, retract, 1);
+				} else
 					break;
 			}
 		}
-		return biggestMove;
+		return ret;
 	}
 	if(retract){
 		bool foundEnd = false;
@@ -225,27 +278,10 @@ int Element_PSTN::MoveStack(Simulation * sim, int stackX, int stackY, int direct
 			return amount;
 		}
 		if(!foundParts && foundEnd)
-			return amount;		
+			return amount;
 	} else {
-		for(posX = stackX, posY = stackY; currentPos < size + amount; posX += directionX, posY += directionY) {
-			if (!(posX < XRES && posY < YRES && posX >= 0 && posY >= 0)) {
-				break;
-			}
-			r = sim->pmap[posY][posX];
-			if(!r) {
-				spaces++;
-				tempParts[currentPos++] = -1;
-				if(spaces >= amount)
-					break;
-			} else {
-				foundParts = true;
-				if(currentPos < size)
-					tempParts[currentPos++] = r>>8;
-				else 
-					break;
-			}
-		}
-		if(foundParts && spaces){
+		currentPos = CanMoveStack(sim, stackX, stackY, directionX, directionY, size, amount);
+		if(currentPos){
 			//Move particles
 			int possibleMovement = 0;
 			for(int j = currentPos-1; j >= 0; j--) {