diff --git a/frontend/js/i18n/de.js b/frontend/js/i18n/de.js
index 692d7cd..f9a0166 100644
--- a/frontend/js/i18n/de.js
+++ b/frontend/js/i18n/de.js
@@ -126,6 +126,8 @@ export default {
   'dashboard.prompt_group_name': 'Gruppenname:',
   'dashboard.error_pairing_code': 'Geben Sie einen gültigen 6-stelligen Kopplungscode ein',
   'dashboard.confirm_add_to_group': '{name} ist bereits in: {groups}\n\nAuch zu „{target}“ hinzufügen?',
+  'dashboard.confirm_move_to_group': '{name} ist derzeit in: {groups}\n\nNach "{target}" verschieben?',
+  'dashboard.toast.move_partial': 'Entfernen aus {group} fehlgeschlagen — Bildschirm ist noch in beiden',
   'dashboard.confirm_assign_playlist': 'Playlist „{playlist}“ allen Geräten in „{group}“ zuweisen?',
   'dashboard.confirm_destructive_command': '{cmd} alle {n} Geräte in „{group}“?\n\nDies kann nicht rückgängig gemacht werden.',
   'dashboard.confirm_delete_group': 'Diese Gruppe löschen? Geräte sind nicht betroffen.',
diff --git a/frontend/js/i18n/en.js b/frontend/js/i18n/en.js
index 4aaead6..b43a047 100644
--- a/frontend/js/i18n/en.js
+++ b/frontend/js/i18n/en.js
@@ -223,6 +223,8 @@ export default {
   'dashboard.prompt_group_name': 'Group name:',
   'dashboard.error_pairing_code': 'Enter a valid 6-digit pairing code',
   'dashboard.confirm_add_to_group': '{name} is already in: {groups}\n\nAdd it to "{target}" too?',
+  'dashboard.confirm_move_to_group': '{name} is currently in: {groups}\n\nMove it to "{target}"?',
+  'dashboard.toast.move_partial': 'Could not remove it from {group} — it is still in both',
   'dashboard.confirm_assign_playlist': 'Assign playlist "{playlist}" to all devices in "{group}"?',
   'dashboard.confirm_destructive_command': '{cmd} all {n} devices in "{group}"?\n\nThis cannot be undone.',
   'dashboard.confirm_delete_group': 'Delete this group? Devices will not be affected.',
diff --git a/frontend/js/i18n/es.js b/frontend/js/i18n/es.js
index b85d89e..7f75d64 100644
--- a/frontend/js/i18n/es.js
+++ b/frontend/js/i18n/es.js
@@ -126,6 +126,8 @@ export default {
   'dashboard.prompt_group_name': 'Nombre del grupo:',
   'dashboard.error_pairing_code': 'Ingresa un código de vinculación válido de 6 dígitos',
   'dashboard.confirm_add_to_group': '{name} ya está en: {groups}\n\n¿Agregarlo también a "{target}"?',
+  'dashboard.confirm_move_to_group': '{name} está actualmente en: {groups}\n\n¿Moverla a "{target}"?',
+  'dashboard.toast.move_partial': 'No se pudo quitar de {group}: sigue en ambos',
   'dashboard.confirm_assign_playlist': '¿Asignar la lista "{playlist}" a todos los dispositivos de "{group}"?',
   'dashboard.confirm_destructive_command': '¿{cmd} todos los {n} dispositivos de "{group}"?\n\nEsto no se puede deshacer.',
   'dashboard.confirm_delete_group': '¿Eliminar este grupo? Los dispositivos no se verán afectados.',
diff --git a/frontend/js/i18n/fr.js b/frontend/js/i18n/fr.js
index 57ac05a..29b237f 100644
--- a/frontend/js/i18n/fr.js
+++ b/frontend/js/i18n/fr.js
@@ -126,6 +126,8 @@ export default {
   'dashboard.prompt_group_name': 'Nom du groupe :',
   'dashboard.error_pairing_code': 'Saisissez un code d\'appairage valide à 6 chiffres',
   'dashboard.confirm_add_to_group': '{name} est déjà dans : {groups}\n\nL\'ajouter aussi à « {target} » ?',
+  'dashboard.confirm_move_to_group': '{name} est actuellement dans : {groups}\n\nLe déplacer vers "{target}" ?',
+  'dashboard.toast.move_partial': 'Impossible de le retirer de {group} — il est encore dans les deux',
   'dashboard.confirm_assign_playlist': 'Attribuer la liste « {playlist} » à tous les appareils de « {group} » ?',
   'dashboard.confirm_destructive_command': '{cmd} les {n} appareils de « {group} » ?\n\nCette action est irréversible.',
   'dashboard.confirm_delete_group': 'Supprimer ce groupe ? Les appareils ne seront pas affectés.',
diff --git a/frontend/js/i18n/it.js b/frontend/js/i18n/it.js
index ce6a98f..99d3bab 100644
--- a/frontend/js/i18n/it.js
+++ b/frontend/js/i18n/it.js
@@ -127,6 +127,8 @@ export default {
   'dashboard.prompt_group_name': 'Nome gruppo:',
   'dashboard.error_pairing_code': 'Inserisci un codice di associazione valido di 6 cifre',
   'dashboard.confirm_add_to_group': '{name} è già presente in: {groups}\n\nAggiungerlo anche a "{target}"?',
+  'dashboard.confirm_move_to_group': '{name} è attualmente in: {groups}\n\nSpostarlo in "{target}"?',
+  'dashboard.toast.move_partial': 'Impossibile rimuoverlo da {group}: è ancora in entrambi',
   'dashboard.confirm_assign_playlist': 'Assegnare la playlist "{playlist}" a tutti i dispositivi in "{group}"?',
   'dashboard.confirm_destructive_command': 'Eseguire {cmd} su tutti i {n} dispositivi in "{group}"?\n\nL\'azione è irreversibile.',
   'dashboard.confirm_delete_group': 'Eliminare questo gruppo? I dispositivi non verranno rimossi dal sistema.',
diff --git a/frontend/js/i18n/pt.js b/frontend/js/i18n/pt.js
index 3d78ab5..50335fa 100644
--- a/frontend/js/i18n/pt.js
+++ b/frontend/js/i18n/pt.js
@@ -126,6 +126,8 @@ export default {
   'dashboard.prompt_group_name': 'Nome do grupo:',
   'dashboard.error_pairing_code': 'Digite um código de pareamento válido de 6 dígitos',
   'dashboard.confirm_add_to_group': '{name} já está em: {groups}\n\nAdicionar também a "{target}"?',
+  'dashboard.confirm_move_to_group': '{name} está atualmente em: {groups}\n\nMover para "{target}"?',
+  'dashboard.toast.move_partial': 'Não foi possível remover de {group} — continua em ambos',
   'dashboard.confirm_assign_playlist': 'Atribuir a playlist "{playlist}" a todos os dispositivos de "{group}"?',
   'dashboard.confirm_destructive_command': '{cmd} todos os {n} dispositivos de "{group}"?\n\nIsso não pode ser desfeito.',
   'dashboard.confirm_delete_group': 'Excluir este grupo? Os dispositivos não serão afetados.',
diff --git a/frontend/js/views/dashboard.js b/frontend/js/views/dashboard.js
index 252e629..60232dd 100644
--- a/frontend/js/views/dashboard.js
+++ b/frontend/js/views/dashboard.js
@@ -767,13 +767,28 @@ function attachGroupHandlers(groupsWithDevices, allDevices) {
         showToast(t('dashboard.toast.already_in_group', { name: deviceName, group: targetGroup.name }), 'info');
         return;
       }
-      // If the device is in another group, mirror the Manage modal's confirm.
-      const others = (groupsByDeviceId.get(deviceId) || []).map(g => g.name);
+      // Dragging a screen onto a group MOVES it. This used to borrow the Manage modal's
+      // "add it too?" confirm and then only add — so the screen ended up in both groups while the
+      // toast claimed it had moved, the page still showed the old group, and a second attempt said
+      // "already in group 2". Reported by a customer doing exactly that with two screens.
+      // The Manage modal keeps add/remove checkboxes: multi-group membership is deliberate THERE.
+      // It is not deliberate here, and it is not harmless — deviceSyncGroup() picks arbitrarily
+      // when a device is in several sync-enabled groups, so a half-move leaves sync ambiguous.
+      const others = groupsByDeviceId.get(deviceId) || [];
       if (others.length > 0) {
-        if (!confirm(t('dashboard.confirm_add_to_group', { name: deviceName, groups: others.join(', '), target: targetGroup.name }))) return;
+        if (!confirm(t('dashboard.confirm_move_to_group', {
+          name: deviceName, groups: others.map(g => g.name).join(', '), target: targetGroup.name,
+        }))) return;
       }
       try {
+        // Add first, then drop the old memberships: if the add fails the screen keeps the group it
+        // had rather than being left ungrouped by a half-finished move.
         await api.addDeviceToGroup(groupId, deviceId);
+        for (const g of others) {
+          if (g.id === groupId) continue;
+          try { await api.removeDeviceFromGroup(g.id, deviceId); }
+          catch (e) { showToast(t('dashboard.toast.move_partial', { group: g.name }), 'warning'); }
+        }
         showToast(t('dashboard.toast.moved_device', { name: deviceName, group: targetGroup.name }), 'success');
         loadDashboard();
       } catch (err) { showToast(err.message, 'error'); }