I get this error in the reports-log:
Message: Cannot modify header information - headers already sent by (output started at /xxx/sites/all/modules/boost/boost.module:4238) in /usr/share/phpbb3/www/includes/session.php on line 1007.
This error is thrown by the cron_crawler, not for normal page views. I have installed the module "phpBBforum Integration module", which integrates the forum directly in the site. It seems to be a compatibility issue. It seems to be similar to the issue.
When I call the URL as in the error message, the header is written by boost with the output "async". After that the phpbb module tries to write another header and the error is thrown. The phpbb module sets another cookie and writes an own header using the header() function from php. I already exluded the phpbbforum pages from the boost caching, but the blocks from the ppbb module are in every page.
How can this problem be solved or the error prevented?