PPPoE disconnected and won't re-connect successfully unless backup/restore

My router often disconnects suddenly and won't auto reconnect anymore. This has happened a few times. I tried to find out the pattern, but it seems to be random.

Major error I saw is pppoe waiting for PADO packet time out.

Sat Jan 22 11:46:11 2022 daemon.warn pppd[16890]: Timeout waiting for PADO packets
Sat Jan 22 11:46:11 2022 daemon.err pppd[16890]: Unable to complete PPPoE Discovery

The only workaround is to backup/restore the configs. This also makes me think it's not really the ppp issue. As I always backup when having this issue and restore immediately. It worked normally after the restore.

I have tried the following but didn't work:

  • Power cycle the router
  • Power cycle the modem
  • Restart network by /etc/init.d/network restart
  • Clone MAC or not makes no difference when having the issue
  • Also tried to tune the LCP threshold/interval

Any clue why? Or are there any other logs or ways to figure out why?

Information:
Device: Netgear Nighthawk X4S R7800
Version: 21.02 (compiled from this source)
Syslogs:

Sat Jan 22 11:45:56 2022 daemon.info pppd[16890]: Plugin pppoe.so loaded.
Sat Jan 22 11:45:56 2022 daemon.info pppd[16890]: PPPoE plugin from pppd 2.4.9
Sat Jan 22 11:45:56 2022 daemon.notice pppd[16890]: pppd 2.4.9 started by root, uid 0
Sat Jan 22 11:46:08 2022 daemon.info dnsmasq[22498]: read /etc/hosts - 4 addresses
Sat Jan 22 11:46:08 2022 daemon.info dnsmasq[22498]: read /tmp/hosts/dhcp.cfg01411c - 9 addresses
Sat Jan 22 11:46:08 2022 daemon.info dnsmasq[22498]: read /tmp/hosts/odhcpd - 4 addresses
Sat Jan 22 11:46:08 2022 daemon.info dnsmasq-dhcp[22498]: read /etc/ethers - 0 addresses
Sat Jan 22 11:46:11 2022 daemon.warn pppd[16890]: Timeout waiting for PADO packets
Sat Jan 22 11:46:11 2022 daemon.err pppd[16890]: Unable to complete PPPoE Discovery
Sat Jan 22 11:46:11 2022 daemon.info pppd[16890]: Exit.
Sat Jan 22 11:46:11 2022 daemon.notice netifd: Interface 'wan' is now down
Sat Jan 22 11:46:11 2022 daemon.notice netifd: Interface 'wan' is disabled
Sat Jan 22 11:46:11 2022 kern.info kernel: [221404.084413] ipq806x-gmac-dwmac 37200000.ethernet eth0: Link is Down
Sat Jan 22 11:46:11 2022 kern.info kernel: [221404.086734] dwmac1000: Master AXI performs any burst length
Sat Jan 22 11:46:11 2022 kern.info kernel: [221404.089837] ipq806x-gmac-dwmac 37200000.ethernet eth0: No Safety Features support found
Sat Jan 22 11:46:11 2022 kern.info kernel: [221404.106661] ipq806x-gmac-dwmac 37200000.ethernet eth0: IEEE 1588-2008 Advanced Timestamp supported
Sat Jan 22 11:46:11 2022 kern.info kernel: [221404.106782] ipq806x-gmac-dwmac 37200000.ethernet eth0: registered PTP clock
Sat Jan 22 11:46:11 2022 kern.info kernel: [221404.116156] ipq806x-gmac-dwmac 37200000.ethernet eth0: configuring for fixed/rgmii link mode
Sat Jan 22 11:46:11 2022 daemon.notice netifd: Interface 'wan' is enabled
Sat Jan 22 11:46:11 2022 daemon.notice netifd: Interface 'wan' is setting up now
Sat Jan 22 11:46:11 2022 kern.info kernel: [221404.123288] ipq806x-gmac-dwmac 37200000.ethernet eth0: Link is Up - 1Gbps/Full - flow control off
Sat Jan 22 11:46:11 2022 kern.info kernel: [221404.139286] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
Sat Jan 22 11:46:11 2022 kern.info kernel: [221404.139529] IPv6: ADDRCONF(NETDEV_CHANGE): eth0.2: link becomes ready
Sat Jan 22 11:46:11 2022 daemon.err insmod: module is already loaded - slhc
Sat Jan 22 11:46:11 2022 daemon.err insmod: module is already loaded - ppp_generic
Sat Jan 22 11:46:11 2022 daemon.err insmod: module is already loaded - pppox
Sat Jan 22 11:46:11 2022 daemon.err insmod: module is already loaded - pppoe
Sat Jan 22 11:46:11 2022 daemon.notice netifd: wan (17120): uci: Entry not found
Sat Jan 22 11:46:11 2022 daemon.info pppd[17165]: Plugin pppoe.so loaded.
Sat Jan 22 11:46:11 2022 daemon.info pppd[17165]: PPPoE plugin from pppd 2.4.9
Sat Jan 22 11:46:11 2022 daemon.notice pppd[17165]: pppd 2.4.9 started by root, uid 0
Sat Jan 22 11:46:26 2022 daemon.warn pppd[17165]: Timeout waiting for PADO packets
Sat Jan 22 11:46:26 2022 daemon.err pppd[17165]: Unable to complete PPPoE Discovery
Sat Jan 22 11:46:26 2022 daemon.info pppd[17165]: Exit.
Sat Jan 22 11:46:27 2022 daemon.notice netifd: Interface 'wan' is now down
Sat Jan 22 11:46:27 2022 daemon.notice netifd: Interface 'wan' is disabled
Sat Jan 22 11:46:27 2022 kern.info kernel: [221419.494363] ipq806x-gmac-dwmac 37200000.ethernet eth0: Link is Down
Sat Jan 22 11:46:27 2022 kern.info kernel: [221419.496664] dwmac1000: Master AXI performs any burst length
Sat Jan 22 11:46:27 2022 kern.info kernel: [221419.499802] ipq806x-gmac-dwmac 37200000.ethernet eth0: No Safety Features support found
Sat Jan 22 11:46:27 2022 kern.info kernel: [221419.516608] ipq806x-gmac-dwmac 37200000.ethernet eth0: IEEE 1588-2008 Advanced Timestamp supported
Sat Jan 22 11:46:27 2022 kern.info kernel: [221419.516765] ipq806x-gmac-dwmac 37200000.ethernet eth0: registered PTP clock
Sat Jan 22 11:46:27 2022 kern.info kernel: [221419.524548] ipq806x-gmac-dwmac 37200000.ethernet eth0: configuring for fixed/rgmii link mode
Sat Jan 22 11:46:27 2022 kern.info kernel: [221419.535965] ipq806x-gmac-dwmac 37200000.ethernet eth0: Link is Up - 1Gbps/Full - flow control off
Sat Jan 22 11:46:27 2022 kern.info kernel: [221419.540566] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
Sat Jan 22 11:46:27 2022 daemon.notice netifd: Interface 'wan' is enabled
Sat Jan 22 11:46:27 2022 daemon.notice netifd: Interface 'wan' is setting up now
Sat Jan 22 11:46:27 2022 daemon.err insmod: module is already loaded - slhc
Sat Jan 22 11:46:27 2022 daemon.err insmod: module is already loaded - ppp_generic
Sat Jan 22 11:46:27 2022 daemon.err insmod: module is already loaded - pppox
Sat Jan 22 11:46:27 2022 daemon.err insmod: module is already loaded - pppoe
Sat Jan 22 11:46:27 2022 daemon.notice netifd: wan (17483): uci: Entry not found

Try the official stable version, or you should seek advice from the maintainer. It is hard to troubleshoot custom versions.