@Phereal:
Hi,
solved this issue by killing the PHP-FPM process by selecting point "16) Restart PHP-FPM" in the ssh menu. Afterwards navigate directly to the address -> https://<ip_address:port>/system_update_settings.php and disable the automatic dashboard auto-update check. Save settings and return to the dashboard.
Now again kill the PHP-FPM process via ssh and reload the page. Afterwards remove the "traffic-graph" widget from the dashboard. Reboot the system to verify your changes.
Now everything should working fine again. Seems like an PHP-module causing trouble.
EDIT: other posts mention problems with some widgets [IP-SEC], if your problems remain, the solution might be to remove all your widgets and then perform a restart.
Afterwards it might be possible to add the widgets again.</ip_address:port>
Had the same issues and followed the solution proposed by Phereal and it worked. Just wanted to say that if at some point you feel your pfsense is stuck just use 16 on console (obviously not when you will be saving your settings).
Thx,