diff --git a/autocrafter.lua b/autocrafter.lua
index c020c49..6134e03 100644
--- a/autocrafter.lua
+++ b/autocrafter.lua
@@ -193,8 +193,9 @@ local function update_meta(meta, enabled)
 			"listring[context;dst]" ..
 			"listring[current_player;main]"
 	if minetest.get_modpath("digilines") then
-		fs = fs.."field[1,3.5;4,1;channel;"..S("Channel")..";${channel}]"
-		fs = fs.."button_exit[5,3.2;2,1;save;"..S("Save").."]"
+		fs = fs.."field[0.3,3.5;4.5,1;channel;"..S("Channel")..";${channel}]"..
+			"button[4.5,3.2;1.5,1;set_channel;"..S("Set").."]"..
+			"button_exit[6,3.2;2,1;close;"..S("Close").."]"
 	end
 	meta:set_string("formspec",fs)
 
@@ -279,7 +280,7 @@ minetest.register_node("pipeworks:autocrafter", {
 		update_meta(meta, false)
 	end,
 	on_receive_fields = function(pos, formname, fields, sender)
-		if (fields.quit and not fields.key_enter_field)
+		if not fields.channel or (fields.quit and not fields.key_enter_field)
 				or not pipeworks.may_configure(pos, sender) then
 			return
 		end
@@ -291,8 +292,9 @@ minetest.register_node("pipeworks:autocrafter", {
 			if update_meta(meta, true) then
 				start_crafter(pos)
 			end
-		elseif fields.save then
-			meta:set_string("channel",fields.channel)
+		end
+		if fields.channel then
+			meta:set_string("channel", fields.channel)
 		end
 	end,
 	can_dig = function(pos, player)
diff --git a/init.lua b/init.lua
index f14b3ba..beeefb7 100644
--- a/init.lua
+++ b/init.lua
@@ -151,7 +151,7 @@ minetest.register_alias("pipeworks:pipe", "pipeworks:pipe_110000_empty")
 
 -- Unified Inventory categories integration
 
-if unified_inventory and unified_inventory.registered_categories then
+if minetest.global_exists("unified_inventory") and unified_inventory.registered_categories then
 	if not unified_inventory.registered_categories["automation"] then
 		unified_inventory.register_category("automation", {
 			symbol = "pipeworks:lua_tube000000",
diff --git a/teleport_tube.lua b/teleport_tube.lua
index 0960a47..e812b70 100644
--- a/teleport_tube.lua
+++ b/teleport_tube.lua
@@ -4,6 +4,9 @@ local filename=minetest.get_worldpath() .. "/teleport_tubes"
 local tp_tube_db = nil -- nil forces a read
 local tp_tube_db_version = 2.0
 
+-- cached rceiver list: hash(pos) => {receivers}
+local cache = {}
+
 local function hash(pos)
 	return string.format("%.30g", minetest.hash_node_position(pos))
 end
@@ -18,6 +21,8 @@ local function save_tube_db()
 	else
 		error(err)
 	end
+	-- reset tp-tube cache
+	cache = {}
 end
 
 local function migrate_tube_db()
@@ -101,6 +106,12 @@ local function read_node_with_vm(pos)
 end
 
 local function get_receivers(pos, channel)
+	local hash = minetest.hash_node_position(pos)
+	if cache[hash] then
+		-- re-use cached result
+		return cache[hash]
+	end
+
 	local tubes = tp_tube_db or read_tube_db()
 	local receivers = {}
 	local dirty = false
@@ -121,6 +132,8 @@ local function get_receivers(pos, channel)
 	if dirty then
 		save_tube_db()
 	end
+	-- cache the result for next time
+	cache[hash] = receivers
 	return receivers
 end