Firewall dies

I have a WL500G with Asus Firmware 19.5.0. The router internet firewall is set to the basic config. After an interval of 7-10 days after re-boot, firewall filtering stops according to the log, but the router continues to check the time at the NTP server.

Here's a typical log:
Oct 29 18:46:57 filter: UDP connection denied to 82.22.73.208:6970 from 64.85.66.185:36195
Oct 29 18:46:58 filter: UDP connection denied to 82.22.73.208:6970 from 64.85.66.185:36195
Oct 29 18:46:58 filter: UDP connection denied to 82.22.73.208:6970 from 64.85.66.185:36195
Oct 29 18:46:58 filter: UDP connection denied to 82.22.73.208:6970 from 64.85.66.185:36195
Oct 29 18:46:58 filter: UDP connection denied to 82.22.73.208:6970 from 64.85.66.185:36195
Oct 29 18:56:19 filter: UDP connection denied to 82.22.73.208:6970 from 64.85.66.185:35866
Oct 29 18:56:19 filter: UDP connection denied to 82.22.73.208:6970 from 64.85.66.185:35866
Oct 29 18:56:20 filter: UDP connection denied to 82.22.73.208:6970 from 64.85.66.185:35866
Oct 29 18:56:20 filter: UDP connection denied to 82.22.73.208:6970 from 64.85.66.185:35866
Oct 29 18:56:20 filter: UDP connection denied to 82.22.73.208:6970 from 64.85.66.185:35866
Oct 29 18:56:20 filter: UDP connection denied to 82.22.73.208:6970 from 64.85.66.185:35866
Oct 29 18:57:09 ntp client: time is synchronized to time.nist.gov
Oct 29 20:57:09 ntp client: time is synchronized to time.nist.gov
Oct 29 22:57:10 ntp client: time is synchronized to time.nist.gov
Oct 30 00:57:10 ntp client: time is synchronized to time.nist.gov
Oct 30 02:57:10 ntp client: time is synchronized to time.nist.gov
Oct 30 04:57:10 ntp client: time is synchronized to time.nist.gov
Oct 30 06:57:09 ntp client: time is synchronized to time.nist.gov
Oct 30 08:57:09 ntp client: time is synchronized to time.nist.gov
Oct 30 10:57:09 ntp client: time is synchronized to time.nist.gov
Oct 30 12:57:09 ntp client: time is synchronized to time.nist.gov
Oct 30 14:57:10 ntp client: time is synchronized to time.nist.gov
Oct 30 16:57:10 ntp client: time is synchronized to time.nist.gov
Oct 30 18:57:10 ntp client: time is synchronized to time.nist.gov
Oct 30 20:57:10 ntp client: time is synchronized to time.nist.gov


Any idea what could be causing this?