Improve stuck cron jobs
We have one web server that appears to have it's .ispconfig_lock, in checking the pid (4727) in it does exist in /proc/ (ie. /proc/4727/), but that process is not a previous server.php job. This has been stuck this way for quite some time (many days).
Two ideas come to mind that would improve such situations, 1) check the lock file timestamp and continue execution if it is "old", and 2) check what process is actually being run by the matching pid, and continue execution if it's not another server.php. Of course they can both be used together.