Spinning indicator when applying changes in email builder

Your software
My Mautic version is: 5.0.3
My PHP version is: 8.1.27
My Database type and version is: MariaDB 10.6

Your problem
My problem is: When clicking the checkmark to apply changes, the progress indicator constantly spins and will not stop. The only way to resolve it is to back out of the page and restart the email builder. The changes do actually get saved.

These errors are showing in the log: None in Mautic log, none in PHP log.

Steps I have tried to fix the problem: PHP INI settings are optimized for Mautic. Happens on two different domains (installed in subdomain of each, because Mautic installer fails when launched from subfolder – a different problem). My webhost InMotion just moved me anyway to a new VPS with AlmaLinux 8.9.0, but problem remains. Deleted Mautic cache. Tried both GrapesJS and old-style templates. Deleted browser cache and same problem in Chrome and Firefox. Looking in Chrome debugger it stops on uncaught exception "TypeError: History.pushState is not a function. Searched Mautic forums and it looks like there are numerous entries with similar issue and no difinitive solution. This unfortunately makes Mautic unusable in its current state.

We had a similar issue and it turned out to be server specs. What does the server usage show when this problem happens?

We also had a client with an issue with the loading times of emails, which could be related. They had over 1000 emails saved, which was causing long load times, we ended up writing a query that removed all emails older than 1 year and the issue resolved.

I just installed it, so there are only two emails and about 10 contacts. No impact on server load.

Are you clearing cache manually or through the CLI?

Just deleting all files in the cache folder manually via Filezilla or cPanel file manager.

This issue has been entered as a bug in Github: