diff --git a/ghost/admin/app/components/gh-site-iframe.hbs b/ghost/admin/app/components/gh-site-iframe.hbs
index ecb5915eac..29cbbd55cd 100644
--- a/ghost/admin/app/components/gh-site-iframe.hbs
+++ b/ghost/admin/app/components/gh-site-iframe.hbs
@@ -3,6 +3,7 @@
     src={{this.srcUrl}}
     frameborder="0"
     allowtransparency="true"
+    {{did-insert (optional @onInserted)}}
     {{did-insert this.attachMessageListener}}
     {{did-update this.resetSrcAttribute @guid}}
     {{on "load" this.onLoad}}
diff --git a/ghost/admin/app/components/gh-site-iframe.js b/ghost/admin/app/components/gh-site-iframe.js
index b689eb2cd1..32f9e7c65f 100644
--- a/ghost/admin/app/components/gh-site-iframe.js
+++ b/ghost/admin/app/components/gh-site-iframe.js
@@ -62,11 +62,15 @@ export default class GhSiteIframeComponent extends Component {
     attachMessageListener() {
         if (typeof this.args.invisibleUntilLoaded === 'string') {
             this.messageListener = (event) => {
+                if (this.isDestroying || this.isDestroyed) {
+                    return;
+                }
+
                 const srcURL = new URL(this.srcUrl);
                 const originURL = new URL(event.origin);
 
                 if (originURL.origin === srcURL.origin) {
-                    if (event.data === this.args.invisibleUntilLoaded) {
+                    if (event.data === this.args.invisibleUntilLoaded || event.data.type === this.args.invisibleUntilLoaded) {
                         this.makeVisible.perform();
                     }
                 }
diff --git a/ghost/admin/app/controllers/settings/membership.js b/ghost/admin/app/controllers/settings/membership.js
index 9f82849d1b..ad9d2536ee 100644
--- a/ghost/admin/app/controllers/settings/membership.js
+++ b/ghost/admin/app/controllers/settings/membership.js
@@ -4,7 +4,6 @@ import {action} from '@ember/object';
 import {currencies, getCurrencyOptions, getSymbol} from 'ghost-admin/utils/currency';
 import {inject as service} from '@ember/service';
 import {task} from 'ember-concurrency-decorators';
-import {timeout} from 'ember-concurrency';
 import {tracked} from '@glimmer/tracking';
 
 const CURRENCIES = currencies.map((currency) => {
@@ -241,20 +240,36 @@ export default class MembersAccessController extends Controller {
         newUrl.searchParams.set('v', this.portalPreviewGuid);
 
         this.portalPreviewUrl = newUrl;
-
-        this.resizePortalPreviewTask.perform();
     }
 
     @action
-    portalPreviewLoaded(iframe) {
+    portalPreviewInserted(iframe) {
         this.portalPreviewIframe = iframe;
-        this.resizePortalPreviewTask.perform();
+
+        if (!this.portalMessageListener) {
+            this.portalMessageListener = (event) => {
+                // don't resize membership portal preview when events fire in customize portal modal
+                if (this.showPortalSettings) {
+                    return;
+                }
+
+                const resizeEvents = ['portal-ready', 'portal-preview-updated'];
+                if (resizeEvents.includes(event.data.type) && event.data.payload?.height) {
+                    this.portalPreviewIframe.parentNode.style.height = `${event.data.payload.height}px`;
+                }
+            };
+
+            window.addEventListener('message', this.portalMessageListener, true);
+        }
     }
 
     @action
     portalPreviewDestroyed() {
         this.portalPreviewIframe = null;
-        this.resizePortalPreviewTask.cancelAll();
+
+        if (this.portalMessageListener) {
+            window.removeEventListener('message', this.portalMessageListener);
+        }
     }
 
     @task
@@ -262,37 +277,6 @@ export default class MembersAccessController extends Controller {
         return yield this.saveSettingsTask.perform({forceRefresh: true});
     }
 
-    @task({restartable: true})
-    *resizePortalPreviewTask() {
-        if (this.portalPreviewIframe && this.portalPreviewIframe.contentWindow) {
-            yield timeout(100); // give time for portal to re-render
-
-            try {
-                const portalIframe = this.portalPreviewIframe.contentWindow.document.querySelector('#ghost-portal-root iframe');
-                if (!portalIframe) {
-                    return;
-                }
-
-                portalIframe.contentWindow.document.body.style.overflow = 'hidden';
-                portalIframe.contentWindow.document.body.style['scrollbar-width'] = 'none';
-
-                const portalContainer = portalIframe.contentWindow.document.querySelector('.gh-portal-popup-container');
-                if (!portalContainer) {
-                    return;
-                }
-
-                const height = portalContainer.clientHeight;
-                this.portalPreviewIframe.parentNode.style.height = `${height}px`;
-            } catch (e) {
-                if (e.name === 'SecurityError') {
-                    // cross-origin blocked
-                    return;
-                }
-                throw e;
-            }
-        }
-    }
-
     async saveProduct() {
         const isStripeConnected = this.settings.get('stripeConnectAccountId');
         if (this.product && isStripeConnected) {
diff --git a/ghost/admin/app/templates/settings/membership.hbs b/ghost/admin/app/templates/settings/membership.hbs
index b8fdbcbe6f..ed052ff1e8 100644
--- a/ghost/admin/app/templates/settings/membership.hbs
+++ b/ghost/admin/app/templates/settings/membership.hbs
@@ -59,7 +59,7 @@
                             scrolling="no"
                             @src={{this.portalPreviewUrl}}
                             @invisibleUntilLoaded="portal-ready"
-                            @onLoad={{this.portalPreviewLoaded}}
+                            @onInserted={{this.portalPreviewInserted}}
                             @onDestroyed={{this.portalPreviewDestroyed}} />
                     {{/if}}
                 </div>