It's a phpBB bug, you can read more about it here: https://tracker.phpbb.com/browse/PHPBB3-14483. A temporary workaround is described here:...
Type: Posts; User: karl94
It's a phpBB bug, you can read more about it here: https://tracker.phpbb.com/browse/PHPBB3-14483. A temporary workaround is described here:...
Try to add
RewriteBase /forum/just below RewriteEngine on.