diff --git a/maidroid/api.lua b/maidroid/api.lua
index f5f4efc..0607007 100644
--- a/maidroid/api.lua
+++ b/maidroid/api.lua
@@ -264,7 +264,7 @@ do
 			if maidroid.is_maidroid(luaentity.name) then
 				local stack = luaentity:get_wield_item_stack()
 
-				if stack:get_name() ~= itemname then
+				if stack:get_name() ~= self.itemname then
 					if stack:is_empty() then
 						self.itemname = ""
 						self.object:set_properties{textures={"maidroid:dummy_empty_craftitem"}}
@@ -448,7 +448,7 @@ function maidroid.register_maidroid(product_name, def)
 			local wield_item = data["inventory"]["wield_item"]
 
 			if core_name ~= "" then -- set a core
-				core_stack = ItemStack(core_name)
+				local core_stack = ItemStack(core_name)
 				core_stack:set_count(1)
 				inventory:add_item("core", core_stack)
 				self.core_name = core_name
@@ -518,7 +518,7 @@ function maidroid.register_maidroid(product_name, def)
 	end
 
 	-- maidroid.maidroid.pickup_item pickup items placed and put it to main slot.
-	function pickup_item(self)
+	local function pickup_item(self)
 		local pos = self.object:getpos()
 		local radius = 1.0
 		local all_objects = minetest.get_objects_inside_radius(pos, radius)
@@ -527,8 +527,7 @@ function maidroid.register_maidroid(product_name, def)
 			if not obj:is_player() and obj:get_luaentity() then
 				local itemstring = obj:get_luaentity().itemstring
 
-				if minetest.registered_nodes[itemstring] ~= nil or minetest.registered_items[itemstring] ~= nil
-				or minetest.registered_tools[itemstring] ~= nil or minetest.registered_craftitems[itemstring] ~= nil then
+				if minetest.registered_items[itemstring] ~= nil then
 					local inv = self:get_inventory()
 					local stack = ItemStack(itemstring)
 					local leftover = inv:add_item("main", stack)
diff --git a/maidroid_core/cores/basic.lua b/maidroid_core/cores/basic.lua
index 3d4ecbd..6fb48bc 100644
--- a/maidroid_core/cores/basic.lua
+++ b/maidroid_core/cores/basic.lua
@@ -16,10 +16,6 @@ local function on_stop(self)
 	self.object:setvelocity{x = 0, y = 0, z = 0}
 end
 
-local on_resume = on_start
-
-local on_pause = on_stop
-
 local function on_step(self, dtime)
 	local player = self:get_nearest_player(10)
 	if player == nil then
@@ -50,7 +46,8 @@ local function on_step(self, dtime)
 	-- if maidroid is stoped by obstacle, the maidroid must jump.
 	if velocity.y == 0 and self.state == state.ACCOMPANY then
 		local front_node = self:get_front_node()
-		if front_node.name ~= "air" then
+		if front_node.name ~= "air" and minetest.registered_nodes[front_node.name] ~= nil
+		and minetest.registered_nodes[front_node.name].walkable then
 			self.object:setvelocity{x = direction.x, y = 5, z = direction.z}
 		end
 	end
@@ -62,7 +59,7 @@ maidroid.register_core("maidroid_core:basic", {
 	inventory_image  = "maidroid_core_basic.png",
 	on_start         = on_start,
 	on_stop          = on_stop,
-	on_resume        = on_resume,
-	on_pause         = on_pause,
+	on_resume        = on_start,
+	on_pause         = on_stop,
 	on_step          = on_step,
 })
diff --git a/maidroid_core/cores/farming.lua b/maidroid_core/cores/farming.lua
index b2a70f1..884e0ae 100644
--- a/maidroid_core/cores/farming.lua
+++ b/maidroid_core/cores/farming.lua
@@ -113,8 +113,11 @@ walk_randomly = function(self, dtime)
 		local velocity = self.object:getvelocity()
 		if velocity.y == 0 then
 			local front_node = self:get_front_node()
-			if front_node.name ~= "air" and minetest.registered_nodes[front_node.name].walkable
-			and not (minetest.get_item_group(front_node.name, "fence") > 0) then
+
+			if minetest.get_item_group(front_node.name, "fence") > 0 then
+				self:change_direction_randomly()
+			elseif front_node.name ~= "air" and minetest.registered_nodes[front_node.name] ~= nil
+			and minetest.registered_nodes[front_node.name].walkable then
 				self.object:setvelocity{x = velocity.x, y = 6, z = velocity.z}
 			end
 		end
@@ -224,7 +227,8 @@ walk_to_plant_and_mow_common = function(self, dtime)
 		local velocity = self.object:getvelocity()
 		if velocity.y == 0 then
 			local front_node = self:get_front_node()
-			if front_node.name ~= "air" and minetest.registered_nodes[front_node.name].walkable
+			if front_node.name ~= "air" and minetest.registered_nodes[front_node.name] ~= nil
+			and minetest.registered_nodes[front_node.name].walkable
 			and not (minetest.get_item_group(front_node.name, "fence") > 0) then
 				self.object:setvelocity{x = velocity.x, y = 6, z = velocity.z}
 			end