diff --git a/DiscoverUM3Action.py b/DiscoverUM3Action.py
index cda6ea386a..35f4e48c71 100644
--- a/DiscoverUM3Action.py
+++ b/DiscoverUM3Action.py
@@ -52,6 +52,22 @@ class DiscoverUM3Action(MachineAction):
             else:
                 self._network_plugin.startDiscovery()
 
+    @pyqtSlot(str, str)
+    def removeManualPrinter(self, key, address):
+        if not self._network_plugin:
+            return
+
+        self._network_plugin.removeManualPrinter(key, address)
+
+    @pyqtSlot(str, str)
+    def setManualPrinter(self, key, address):
+        if key != "":
+            # This manual printer replaces a current manual printer
+            self._network_plugin.removeManualPrinter(key)
+
+        if address != "":
+            self._network_plugin.addManualPrinter(address)
+
     def _onPrinterDiscoveryChanged(self, *args):
         self._last_zeroconf_event_time = time.time()
         self.printersChanged.emit()
diff --git a/DiscoverUM3Action.qml b/DiscoverUM3Action.qml
index 4079df3f2e..0cd4ba0481 100644
--- a/DiscoverUM3Action.qml
+++ b/DiscoverUM3Action.qml
@@ -96,7 +96,7 @@ Cura.MachineAction
                 id: removeButton
                 text: catalog.i18nc("@action:button", "Remove")
                 enabled: base.selectedPrinter && base.selectedPrinter.getKey().substr(0,7) =="manual:"
-                onClicked: manager.removeManualPrinter(base.selectedPrinter.getKey())
+                onClicked: manager.removeManualPrinter(base.selectedPrinter.getKey(), base.selectedPrinter.ipAddress)
             }
 
             Button
diff --git a/NetworkPrinterOutputDevicePlugin.py b/NetworkPrinterOutputDevicePlugin.py
index f1d5acefef..83416c4fc6 100644
--- a/NetworkPrinterOutputDevicePlugin.py
+++ b/NetworkPrinterOutputDevicePlugin.py
@@ -39,9 +39,9 @@ class NetworkPrinterOutputDevicePlugin(OutputDevicePlugin):
         Application.getInstance().globalContainerStackChanged.connect(self.reCheckConnections)
 
         # Get list of manual printers from preferences
-        preferences = Preferences.getInstance()
-        preferences.addPreference("um3networkprinting/manual_instances", "") #  A comma-separated list of ip adresses or hostnames
-        self._manual_instances = preferences.getValue("um3networkprinting/manual_instances").split(",")
+        self._preferences = Preferences.getInstance()
+        self._preferences.addPreference("um3networkprinting/manual_instances", "") #  A comma-separated list of ip adresses or hostnames
+        self._manual_instances = self._preferences.getValue("um3networkprinting/manual_instances").split(",")
 
     addPrinterSignal = Signal()
     removePrinterSignal = Signal()
@@ -65,11 +65,17 @@ class NetworkPrinterOutputDevicePlugin(OutputDevicePlugin):
             self.addManualPrinter(address)
 
     def addManualPrinter(self, address):
-        # Add a preliminary printer instance
+        if address not in self._manual_instances:
+            self._manual_instances.append(address)
+            self._preferences.setValue("um3networkprinting/manual_instances", ",".join(self._manual_instances))
+
         name = address
         instance_name = "manual:%s" % address
         properties = { b"name": name.encode("UTF-8") }
-        self.addPrinter(instance_name, address, properties)
+
+        if instance_name not in self._printers:
+            # Add a preliminary printer instance
+            self.addPrinter(instance_name, address, properties)
 
         # Check if a printer exists at this address
         # If a printer responds, it will replace the preliminary printer created above
@@ -77,6 +83,16 @@ class NetworkPrinterOutputDevicePlugin(OutputDevicePlugin):
         name_request = QNetworkRequest(url)
         self._network_manager.get(name_request)
 
+    def removeManualPrinter(self, key, address = None):
+        if key in self._printers:
+            if not address:
+                address = self._printers[key].ipAddress
+            self.removePrinter(key)
+
+        if address in self._manual_instances:
+            self._manual_instances.remove(address)
+            self._preferences.setValue("um3networkprinting/manual_instances", ",".join(self._manual_instances))
+
     ##  Handler for all requests that have finished.
     def _onNetworkRequestFinished(self, reply):
         reply_url = reply.url().toString()
@@ -91,8 +107,10 @@ class NetworkPrinterOutputDevicePlugin(OutputDevicePlugin):
 
                     instance_name = "manual:%s" % address
                     properties = { b"name": name.encode("UTF-8") }
-                    self.removePrinter(instance_name)
-                    self.addPrinter(instance_name, address, properties)
+                    if instance_name in self._printers:
+                        # Only replace the printer if it is still in the list of (manual) printers
+                        self.removePrinter(instance_name)
+                        self.addPrinter(instance_name, address, properties)
 
     ##  Stop looking for devices on network.
     def stop(self):