It took about 5minutes to get that post to submit. tried lots of options but they all came back with the same error
[phpBB Debug] PHP Notice: in file /posting.php on line 666: require(./includes/functions_link_filter.php): failed to open stream: No such file or directory
It does work, but it doesn't always work! This problem has existed for a good year or more, but the Forum administrators seem to not be interested in fixing it. The error may be suggestive of the PHP environment running out of file handles. Retrying the submit will work only when the reason for the failure has abated and since you don't know when that is you just have to keep retrying. I'm getting the error trying to submit this post!