diff --git a/manager/display.lua b/manager/display.lua
index f1b9707..e2d7916 100644
--- a/manager/display.lua
+++ b/manager/display.lua
@@ -120,7 +120,24 @@ end
 -- Monitor setup
 -------------------------------------------------
 
-local function findMonitor(side, excludeSide)
+--- Check whether two peripheral names refer to the same physical block.
+-- Needed because a monitor placed adjacent to the computer AND connected
+-- via wired modem appears under both its side name (e.g. "left") and its
+-- network name (e.g. "monitor_0").  A simple string comparison misses this.
+local function sameMonitor(a, b)
+    if not a or not b then return false end
+    if a == b then return true end
+    -- Write a distinctive cursor position via one name and read it back
+    -- via the other; if they share state, they are the same peripheral.
+    local ok1 = pcall(peripheral.call, a, "setCursorPos", 9876, 5432)
+    if not ok1 then return false end
+    local ok2, x, y = pcall(peripheral.call, b, "getCursorPos")
+    pcall(peripheral.call, a, "setCursorPos", 1, 1)
+    return ok2 and x == 9876 and y == 5432
+end
+
+local function findMonitor(side, excludeNames)
+    excludeNames = excludeNames or {}
     local mon = peripheral.wrap(side)
     local monName
     if mon and mon.setTextScale then
@@ -130,10 +147,16 @@ local function findMonitor(side, excludeSide)
     end
     if not mon then
         for _, name in ipairs(peripheral.getNames()) do
-            if peripheral.getType(name) == "monitor" and name ~= excludeSide then
-                mon = peripheral.wrap(name)
-                monName = name
-                break
+            if peripheral.getType(name) == "monitor" then
+                local dominated = false
+                for _, ex in ipairs(excludeNames) do
+                    if sameMonitor(name, ex) then dominated = true; break end
+                end
+                if not dominated then
+                    mon = peripheral.wrap(name)
+                    monName = name
+                    break
+                end
             end
         end
     end
@@ -141,7 +164,7 @@ local function findMonitor(side, excludeSide)
 end
 
 function D.setupMonitor()
-    D.mon, D.monName = findMonitor(cfg.MONITOR_SIDE, cfg.SMELTER_MONITOR_SIDE)
+    D.mon, D.monName = findMonitor(cfg.MONITOR_SIDE, { cfg.SMELTER_MONITOR_SIDE })
     if not D.mon then return false end
 
     mainDevice = UI.Device({
@@ -152,7 +175,7 @@ function D.setupMonitor()
 end
 
 function D.setupSmelterMonitor()
-    D.smelterMon, D.smelterMonName = findMonitor(cfg.SMELTER_MONITOR_SIDE, D.monName)
+    D.smelterMon, D.smelterMonName = findMonitor(cfg.SMELTER_MONITOR_SIDE, { D.monName })
     if not D.smelterMon then return false end
 
     smelterDevice = UI.Device({
@@ -178,8 +201,8 @@ function D.setupBillboardMonitor()
     -- Auto-detect: find any monitor not already used by main/smelter
     for _, name in ipairs(peripheral.getNames()) do
         if peripheral.getType(name) == "monitor"
-           and name ~= D.monName
-           and name ~= D.smelterMonName then
+           and not sameMonitor(name, D.monName)
+           and not sameMonitor(name, D.smelterMonName) then
             local mon = peripheral.wrap(name)
             if mon and mon.setTextScale then
                 D.billboardMon = mon