diff --git a/client/src/campaigns/CUD.js b/client/src/campaigns/CUD.js
index c7d014d4..945965a9 100644
--- a/client/src/campaigns/CUD.js
+++ b/client/src/campaigns/CUD.js
@@ -82,7 +82,7 @@ export default class CUD extends Component {
         ];
 
         this.sourceOptions = [];
-        for (const key in sourceLabelsOrder) {
+        for (const key of sourceLabelsOrder) {
             this.sourceOptions.push({key, label: this.sourceLabels[key]});
         }
 
@@ -134,8 +134,9 @@ export default class CUD extends Component {
 
         if (key === 'data_sourceCustom_tag_language') {
             if (newValue) {
+                const currentType = this.getFormValue('data_sourceCustom_type');
                 const isEdit = !!this.props.entity;
-                this.templateTypes[newValue].afterTagLanguageChange(mutStateData, isEdit);
+                this.templateTypes[currentType].afterTagLanguageChange(mutStateData, isEdit);
             }
         }
 
diff --git a/client/src/campaigns/Content.js b/client/src/campaigns/Content.js
index 4d218cd8..4880538a 100644
--- a/client/src/campaigns/Content.js
+++ b/client/src/campaigns/Content.js
@@ -83,8 +83,8 @@ export default class CustomContent extends Component {
 
     onTagLanguageChanged(mutStateData, key, oldTagLanguage, tagLanguage) {
         if (tagLanguage) {
-            const type = mutStateData.getIn(['data_sourceCustom_tag_language', 'value']);
-            this.tagLanguages[type].afterTagLanguageChange(mutStateData, true);
+            const type = mutStateData.getIn(['data_sourceCustom_type', 'value']);
+            this.templateTypes[type].afterTagLanguageChange(mutStateData, true);
         }
     }
 
diff --git a/client/src/templates/CUD.js b/client/src/templates/CUD.js
index 39bab165..c89166de 100644
--- a/client/src/templates/CUD.js
+++ b/client/src/templates/CUD.js
@@ -98,9 +98,13 @@ export default class CUD extends Component {
     }
 
     submitFormValuesMutator(data) {
-        this.templateTypes[data.type].beforeSave(data);
+        if (data.fromExistingEntity) {
+            return filterData(data, ['name', 'description', 'namespace', 'fromExistingEntity', 'existingEntity']);
 
-        return filterData(data, ['name', 'description', 'type', 'tag_language', 'data', 'html', 'text', 'namespace', 'fromExistingEntity', 'existingEntity']);
+        } else {
+            this.templateTypes[data.type].beforeSave(data);
+            return filterData(data, ['name', 'description', 'type', 'tag_language', 'data', 'html', 'text', 'namespace', 'fromExistingEntity']);
+        }
     }
 
     async getPreSubmitFormValuesUpdater() {
@@ -151,25 +155,28 @@ export default class CUD extends Component {
             state.setIn(['name', 'error'], t('nameMustNotBeEmpty'));
         }
 
-        const typeKey = state.getIn(['type', 'value']);
-        if (!typeKey) {
-            state.setIn(['type', 'error'], t('typeMustBeSelected'));
-        }
-
-        if (!state.getIn(['tag_language', 'value'])) {
-            state.setIn(['tag_language', 'error'], t('Tag language must be selected'));
-        }
-
-        if (state.getIn(['fromExistingEntity', 'value']) && !state.getIn(['existingEntity', 'value'])) {
-            state.setIn(['existingEntity', 'error'], t('sourceTemplateMustNotBeEmpty'));
-        } else {
-            state.setIn(['existingEntity', 'error'], null);
-        }
-
         validateNamespace(t, state);
 
-        if (typeKey) {
-            this.templateTypes[typeKey].validate(state);
+        const fromExistingEntity = state.getIn(['fromExistingEntity', 'value']);
+
+        if (fromExistingEntity) {
+            if (!state.getIn(['existingEntity', 'value'])) {
+                state.setIn(['existingEntity', 'error'], t('sourceTemplateMustNotBeEmpty'));
+            }
+
+        } else {
+            const typeKey = state.getIn(['type', 'value']);
+            if (!typeKey) {
+                state.setIn(['type', 'error'], t('typeMustBeSelected'));
+            }
+
+            if (!state.getIn(['tag_language', 'value'])) {
+                state.setIn(['tag_language', 'error'], t('Tag language must be selected'));
+            }
+
+            if (typeKey) {
+                this.templateTypes[typeKey].validate(state);
+            }
         }
     }
 
diff --git a/server/lib/message-sender.js b/server/lib/message-sender.js
index ec90eefd..7b0360ef 100644
--- a/server/lib/message-sender.js
+++ b/server/lib/message-sender.js
@@ -293,6 +293,8 @@ class MessageSender {
         let subscriptionGrouped, list; // May be undefined
         const campaign = this.campaign; // May be undefined
 
+        const sendConfiguration = this.sendConfiguration;
+
         let mergeTags = subData.mergeTags;
 
         if (subData.listId) {
@@ -389,7 +391,6 @@ class MessageSender {
             return;
         }
 
-        const sendConfiguration = this.sendConfiguration;
         const mailer = await mailers.getOrCreateMailer(sendConfiguration.id);
 
         await mailer.throttleWait();
diff --git a/server/models/campaigns.js b/server/models/campaigns.js
index 2e6aaa8f..7c8c5bfa 100644
--- a/server/models/campaigns.js
+++ b/server/models/campaigns.js
@@ -529,7 +529,6 @@ async function _createTx(tx, context, entity, content) {
 
         if (copyFilesFrom) {
             await files.copyAllTx(tx, context, copyFilesFrom.entityType, 'file', copyFilesFrom.entityId, 'campaign', 'file', id);
-
             convertFileURLs(data.sourceCustom, copyFilesFrom.entityType, copyFilesFrom.entityId, 'campaign', id);
             await tx('campaigns')
                 .update({
diff --git a/server/models/templates.js b/server/models/templates.js
index 68d34c28..209e1635 100644
--- a/server/models/templates.js
+++ b/server/models/templates.js
@@ -67,8 +67,6 @@ async function _validateAndPreprocess(tx, entity) {
     enforce(allTagLanguages.includes(entity.tag_language), `Invalid tag language '${entity.tag_language}'`);
 
     // We don't check contents of the "data" because it is processed solely on the client. The client generates the HTML code we use when sending out campaigns.
-
-    entity.data = JSON.stringify(entity.data);
 }
 
 async function create(context, entity) {
@@ -87,7 +85,13 @@ async function create(context, entity) {
 
         await _validateAndPreprocess(tx, entity);
 
-        const ids = await tx('templates').insert(filterObject(entity, allowedKeys));
+        const filteredEntityWithUnstringifiedData = filterObject(entity, allowedKeys);
+        const filteredEntity = {
+            ...filteredEntityWithUnstringifiedData,
+            data: JSON.stringify(filteredEntityWithUnstringifiedData.data)
+        };
+
+        const ids = await tx('templates').insert(filteredEntity);
         const id = ids[0];
 
         await shares.rebuildPermissionsTx(tx, { entityTypeId: 'template', entityId: id });
@@ -95,8 +99,14 @@ async function create(context, entity) {
         if (entity.fromExistingEntity) {
             await files.copyAllTx(tx, context, 'template', 'file', entity.existingEntity, 'template', 'file', id);
 
-            convertFileURLs(entity, 'template', entity.existingEntity, 'template', id);
-            await tx('templates').update(filterObject(entity, allowedKeys)).where('id', id);
+            convertFileURLs(filteredEntityWithUnstringifiedData, 'template', entity.existingEntity, 'template', id);
+
+            const filteredEntity = {
+                ...filteredEntityWithUnstringifiedData,
+                data: JSON.stringify(filteredEntityWithUnstringifiedData.data)
+            };
+
+            await tx('templates').update(filteredEntity).where('id', id);
         }
 
         return id;
@@ -120,10 +130,13 @@ async function updateWithConsistencyCheck(context, entity) {
         }
 
         await _validateAndPreprocess(tx, entity);
+        entity.data = JSON.stringify(entity.data);
 
         await namespaceHelpers.validateMove(context, entity, existing, 'template', 'createTemplate', 'delete');
 
-        await tx('templates').where('id', entity.id).update(filterObject(entity, allowedKeys));
+        const filteredEntity = filterObject(entity, allowedKeys);
+
+        await tx('templates').where('id', entity.id).update(filteredEntity);
 
         await shares.rebuildPermissionsTx(tx, { entityTypeId: 'template', entityId: entity.id });
     });