diff --git a/gate.lua b/gate.lua
index e691c66..4ba0528 100644
--- a/gate.lua
+++ b/gate.lua
@@ -1,9 +1,11 @@
 local DEFAULT_SERVER_BASE = "http://ticket.fse-media.group"
 local DEFAULT_SERVER_PATH = "/api/tickets/check"
 local GATE_OPEN_SECONDS = 2
-local VERSION = "v1.5.18"
+local VERSION = "v1.5.20"
 local VERSION_CHECK_INTERVAL = 5
 
+local serverURL = nil
+
 local CONFIG_PATH = "gate_config.json"
 
 local function readFile(path)
@@ -164,7 +166,7 @@ local function checkAndApplyUpdate()
   
   if not remoteTs or remoteTs <= 0 then return end
   
-  local attemptFile = ".last_update_ts"
+  local attemptFile = ".last_update_ts_gate"
   if fs.exists(attemptFile) then
     local f = fs.open(attemptFile, "r")
     local tried = tonumber(f and f.readAll() or "0") or 0
@@ -175,7 +177,9 @@ local function checkAndApplyUpdate()
   end
 
   isUpdating = true
-  pcall(drawReadyScreen)
+  if type(drawReadyScreen) == "function" then
+    pcall(drawReadyScreen)
+  end
   sleep(0.5)
 
   local f = fs.open(attemptFile, "w")
@@ -203,7 +207,7 @@ local function checkAndApplyUpdate()
   end
   
   isUpdating = false
-  if pcall then
+  if type(drawReadyScreen) == "function" then
     pcall(drawReadyScreen)
   end
   
@@ -784,7 +788,7 @@ end
 
 local cfg = loadConfig()
 local stationSet = stationSetFromList(cfg.station_codes)
-local serverURL = resolveServerURL(cfg)
+serverURL = resolveServerURL(cfg)
 local cardServerURL = resolveCardServerURL(cfg, serverURL)
 local cardSyncBaseURL = resolveCardSyncBaseURL(cfg, serverURL, cardServerURL)
 local fareQueryURL = resolveFareQueryURL(serverURL)
@@ -1500,19 +1504,24 @@ end
 
 local versionTimer = os.startTimer(VERSION_CHECK_INTERVAL)
 
-
-
-while true do
-  local ev = pack(os.pullEvent())
-  if ev[1] == "ticket_scanned" or ev[1] == "ic_card_scanned" then
-    processInspectionEvent(ev[1], ev)
-    os.sleep(0.35)
-    drawReadyScreen()
-  elseif ev[1] == "timer" and ev[2] == versionTimer then
-    pcall(function()
-      refreshRemoteLuaVersion(guessBaseFromStatusURL(serverURL))
-    end)
-    pcall(checkAndApplyUpdate)
-    versionTimer = os.startTimer(VERSION_CHECK_INTERVAL)
+local function mainLoop()
+  while true do
+    local ev = pack(os.pullEvent())
+    if ev[1] == "ticket_scanned" or ev[1] == "ic_card_scanned" then
+      processInspectionEvent(ev[1], ev)
+      os.sleep(0.35)
+      drawReadyScreen()
+    end
   end
 end
+
+local function backgroundSyncTask()
+  pcall(function() refreshRemoteLuaVersion(guessBaseFromStatusURL(serverURL)) end)
+  while true do
+    sleep(VERSION_CHECK_INTERVAL)
+    pcall(function() refreshRemoteLuaVersion(guessBaseFromStatusURL(serverURL)) end)
+    pcall(checkAndApplyUpdate)
+  end
+end
+
+parallel.waitForAny(mainLoop, backgroundSyncTask)
diff --git a/refillmachine.lua b/refillmachine.lua
index 646cb30..f96c97c 100644
--- a/refillmachine.lua
+++ b/refillmachine.lua
@@ -1,4 +1,4 @@
-local VERSION = "v1.5.18"
+local VERSION = "v1.5.20"
 local MACHINE_SIDE = "bottom"
 local PAYMENT_SIDE = "right"
 local PRESET_AMOUNTS = { 5, 10, 15, 20 }
diff --git a/ticketmachine.lua b/ticketmachine.lua
index 4f0d874..ee8b78a 100644
--- a/ticketmachine.lua
+++ b/ticketmachine.lua
@@ -1,6 +1,6 @@
 local CURRENT_STATION_CODE = 'Ticket-Machine'
 local API_BASE = 'http://ticket.fse-media.group/api'
-local VERSION = 'v1.5.18'
+local VERSION = 'v1.5.20'
 local UPDATE_CHECK_INTERVAL = 5
 
 -- ###########################