Failed to send buffer or zlib output compression

Hi,

All of a sudden, there were 2 errors in the website I am developing. I am not really sure what is this. The first error was fixed when I deactivate the WP-CORS plugin.

The second one appeared at the very bottom of the page:

Notice: ob_end_flush(): failed to send buffer of zlib output compression (1) in /home/clients/cea28d9da84c18bfeaf2ef9c055f8290/web/wp-includes/functions.php on line 3730

The page I need help with: [log in to see the link]