pfsense blocking from LAN to OPT after running some days.

[piphat]

After pfsense running for some time, I have an issue accessing from LAN to a host in OPT, to just only one specific host I used to keep backup data which will recieve and send a lot of data everyday. However other hosts in OPT can be accessed normally. No package installed except vmtools.
After rebooted, everything back to normal. Not sure that some kind of limit or something broken.
Traffic captured during having an issue showing that pfsense received packet, but destination host not receiving. Ping from pfsense with LAN source to the host has no problem. Any idea?