[Closed] WPML string translation plugin problem related to the Astra theme

Hello WPML Team,
I am experiencing the following issue on the site:
The Astra theme is running there, and as soon as I activate the WPML String Translation plugin, I can no longer access the customiser (hidden link); the page simply remains blank.
And this error appears in debug.log
[30-Jan-2026 07:41:47 UTC] PHP Fatal error: ob_end_flush(): Cannot use output buffering in output buffering display handlers in /storage/dev/sal002/wordpress/wp-includes/functions.php on line 5481

When I switch to a different theme (Twenty Twenty-Five), the error does not occur and everything continues to work.
I have also tried completely reinstalling WPML, but unfortunately that did not help.
I have also made sure that the plug-ins, theme and WordPress are all the latest versions.
Can anyone please help me with this?

Kind regards