# Builder window does not close in Mautic 5.2.3

**URL:** <https://forum.mautic.org/t/builder-window-does-not-close-in-mautic-5-2-3/35328>\
**Category:** Mautic 5 Install/Upgrade Support\
**Created:** [March 21, 2025, 10:46am UTC](https://forum.mautic.org/t/builder-window-does-not-close-in-mautic-5-2-3/35328 "2025-03-21T10:46:15Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![adrianr1974](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/adrianr1974/32/6591_2.png) [@adrianr1974](https://forum.mautic.org/u/adrianr1974)\
**Post date:** [March 21, 2025, 10:46am UTC](https://forum.mautic.org/t/builder-window-does-not-close-in-mautic-5-2-3/35328/1 "2025-03-21T10:46:15Z")

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**Your software**  
My Mautic version is: 5.2.3  
My PHP version is: 8.3  
My Database type and version is: MariaDB 10.6.21

**Your problem**  
I am migrating from Mautic 4.4.13 to 5.2.3. My understanding is that email templates can only be transferred manually. I copy the Builder code of a given template in the old Mautic version to the new version. I use the Blank theme. After copying the code to the new version and clicking “Apply Changes”, the Builder window will not close. Therefore, I cannot get to the previous window to save the template. What could be the cause of this?

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**Author:** ![serendipitytech](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/serendipitytech/32/13359_2.png) [@serendipitytech](https://forum.mautic.org/u/serendipitytech)\
**Post date:** [April 25, 2025, 5:54pm UTC](https://forum.mautic.org/t/builder-window-does-not-close-in-mautic-5-2-3/35328/2 "2025-04-25T17:54:28Z")

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Hi, I’m a new mautic user, but I’ve experienced similar behavior, and for me it was a malformed JS in the template I was copying. It wasn’t from Mautic 4 to 5, it was a different source, but that was my issue.  
Another user on this forum linked to their site for some templates, and I saw they have a validator, perhaps this can help find the issue?

> **[MJML Validator – Crafting.email](https://crafting.email/mjml-validator/)**
>
> Optimize your MJML code for free with our MJML Validator. Create perfect email templates effortlessly.