which IP to ping every 50 sec ?

[Moat 11]

EDIT (new question): Which IP address is OK to be pinged every 50 seconds and is still privacy/no log OK ? Thanks!

I customized the AirVPN Openwrt config to have the reconnect.sh script point to a specific IP address. The IP address stopped responding to pings 2 days ago. For now, I changed the IP to google, all working again like charm. But I don't like Google ... So looking for an alternative.

Original question "troubleshoot airvpn Interrupted system call (code=4)":

Can anyone please help me troubleshoot my routers?

OpenVPN is disconnecting after ±1 minute and reloading.

I think the issue is:

event_wait : Interrupted system call (code=4)

Conscious of issue since 2-3 days, before with exact same config all seemed to be OK.

Happens on OpenWrt 21.02.1 and on OpenWrt 21.02.0

Openwrt configured using ulmwind's guide

Airvpn config generator specifics:
using generator for "router"
connect with ip layer ipv4
ip layer exit ipv4 only

Log section:

Sat Dec 11 09:48:07 2021 daemon.notice openvpn(OpenWRT)[1620]: Initialization Sequence Completed
Sat Dec 11 09:48:40 2021 kern.info kernel: [   91.160539] rt3050-esw 10110000.esw: link changed 0x00
Sat Dec 11 09:48:54 2021 daemon.err openvpn(OpenWRT)[1620]: event_wait : Interrupted system call (code=4)
Sat Dec 11 09:48:54 2021 daemon.notice openvpn(OpenWRT)[1620]: SIGTERM received, sending exit notification to peer
Sat Dec 11 09:48:59 2021 daemon.notice openvpn(OpenWRT)[1620]: net_route_v4_del: 213.152.161.248/32 via 192.168.1.1 dev [NULL] table 0 metric -1
Sat Dec 11 09:48:59 2021 daemon.notice openvpn(OpenWRT)[1620]: net_route_v4_del: 0.0.0.0/1 via 10.24.168.1 dev [NULL] table 0 metric -1
Sat Dec 11 09:48:59 2021 daemon.notice openvpn(OpenWRT)[1620]: net_route_v4_del: 128.0.0.0/1 via 10.24.168.1 dev [NULL] table 0 metric -1
Sat Dec 11 09:48:59 2021 daemon.notice openvpn(OpenWRT)[1620]: Closing TUN/TAP interface
Sat Dec 11 09:48:59 2021 daemon.notice openvpn(OpenWRT)[1620]: net_addr_v4_del: 10.24.168.174 dev tun0
Sat Dec 11 09:48:59 2021 daemon.notice netifd: Network device 'tun0' link is down
Sat Dec 11 09:48:59 2021 daemon.notice netifd: Interface 'OpenWRT' has link connectivity loss
Sat Dec 11 09:48:59 2021 daemon.notice netifd: Interface 'OpenWRT' is now down
Sat Dec 11 09:48:59 2021 daemon.notice openvpn(OpenWRT)[1620]: /usr/libexec/openvpn-hotplug down OpenWRT tun0 1500 1538 10.24.168.174 255.255.255.0 init
Sat Dec 11 09:48:59 2021 daemon.notice openvpn(OpenWRT)[1620]: SIGTERM[soft,exit-with-notification] received, process exiting
Sat Dec 11 09:48:59 2021 daemon.notice netifd: Interface 'OpenWRT' is disabled
Sat Dec 11 09:48:59 2021 daemon.notice openvpn(OpenWRT)[2454]: OpenVPN 2.5.3 mipsel-openwrt-linux-gnu [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [MH/PKTINFO] [AEAD]
Sat Dec 11 09:48:59 2021 daemon.notice openvpn(OpenWRT)[2454]: library versions: OpenSSL 1.1.1k  25 Mar 2021, LZO 2.10
Sat Dec 11 09:48:59 2021 daemon.warn openvpn(OpenWRT)[2454]: NOTE: the current --script-security setting may allow this configuration to call user-defined scripts
Sat Dec 11 09:48:59 2021 daemon.notice openvpn(OpenWRT)[2454]: Outgoing Control Channel Authentication: Using 160 bit message hash 'SHA1' for HMAC authentication
Sat Dec 11 09:48:59 2021 daemon.notice openvpn(OpenWRT)[2454]: Incoming Control Channel Authentication: Using 160 bit message hash 'SHA1' for HMAC authentication
Sat Dec 11 09:49:02 2021 daemon.notice openvpn(OpenWRT)[2454]: TCP/UDP: Preserving recently used remote address: [AF_INET]141.98.102.242:443
Sat Dec 11 09:49:02 2021 daemon.notice openvpn(OpenWRT)[2454]: Socket Buffers: R=[180224->180224] S=[180224->180224]
Sat Dec 11 09:49:02 2021 daemon.notice openvpn(OpenWRT)[2454]: UDP link local: (not bound)
Sat Dec 11 09:49:02 2021 daemon.notice openvpn(OpenWRT)[2454]: UDP link remote: [AF_INET]141.98.102.242:443
Sat Dec 11 09:49:02 2021 daemon.notice openvpn(OpenWRT)[2454]: TLS: Initial packet from [AF_INET]141.98.102.242:443, sid=2fbf3630 b63934b8
Sat Dec 11 09:49:02 2021 daemon.notice openvpn(OpenWRT)[2454]: VERIFY OK: depth=1, C=IT, ST=IT, L=Perugia, O=airvpn.org, CN=airvpn.org CA, emailAddress=info@airvpn.org
Sat Dec 11 09:49:02 2021 daemon.notice openvpn(OpenWRT)[2454]: VERIFY KU OK
Sat Dec 11 09:49:02 2021 daemon.notice openvpn(OpenWRT)[2454]: Validating certificate extended key usage
Sat Dec 11 09:49:02 2021 daemon.notice openvpn(OpenWRT)[2454]: ++ Certificate has EKU (str) TLS Web Server Authentication, expects TLS Web Server Authentication
Sat Dec 11 09:49:02 2021 daemon.notice openvpn(OpenWRT)[2454]: VERIFY EKU OK
Sat Dec 11 09:49:02 2021 daemon.notice openvpn(OpenWRT)[2454]: VERIFY OK: depth=0, C=IT, ST=IT, L=Perugia, O=airvpn.org, CN=Dubhe, emailAddress=info@airvpn.org
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: Control Channel: TLSv1.3, cipher TLSv1.3 TLS_CHACHA20_POLY1305_SHA256, peer certificate: 4096 bit RSA, signature: RSA-SHA512
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: [Dubhe] Peer Connection Initiated with [AF_INET]141.98.102.242:443
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: PUSH: Received control message: 'PUSH_REPLY,comp-lzo no,redirect-gateway  def1 bypass-dhcp,dhcp-option DNS 10.26.8.1,route-gateway 10.26.8.1,topology subnet,ping 10,ping-restart 60,ifconfig 10.26.8.74 255.255.255.0,peer-id 5,cipher CHACHA20-POLY1305'
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: OPTIONS IMPORT: timers and/or timeouts modified
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: OPTIONS IMPORT: compression parms modified
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: OPTIONS IMPORT: --ifconfig/up options modified
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: OPTIONS IMPORT: route options modified
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: OPTIONS IMPORT: route-related options modified
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: OPTIONS IMPORT: --ip-win32 and/or --dhcp-option options modified
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: OPTIONS IMPORT: peer-id set
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: OPTIONS IMPORT: adjusting link_mtu to 1625
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: OPTIONS IMPORT: data channel crypto options modified
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: Data Channel: using negotiated cipher 'CHACHA20-POLY1305'
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: Outgoing Data Channel: Cipher 'CHACHA20-POLY1305' initialized with 256 bit key
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: Incoming Data Channel: Cipher 'CHACHA20-POLY1305' initialized with 256 bit key
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: net_route_v4_best_gw query: dst 0.0.0.0
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: net_route_v4_best_gw result: via 192.168.1.1 dev wlan0
Sat Dec 11 09:49:03 2021 daemon.notice netifd: Interface 'OpenWRT' is enabled
Sat Dec 11 09:49:03 2021 daemon.notice netifd: Network device 'tun0' link is up
Sat Dec 11 09:49:03 2021 daemon.notice netifd: Interface 'OpenWRT' has link connectivity
Sat Dec 11 09:49:03 2021 daemon.notice netifd: Interface 'OpenWRT' is setting up now
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: TUN/TAP device tun0 opened
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: net_iface_mtu_set: mtu 1500 for tun0
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: net_iface_up: set tun0 up
Sat Dec 11 09:49:03 2021 daemon.notice netifd: Interface 'OpenWRT' is now up
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: net_addr_v4_add: 10.26.8.74/24 dev tun0
Sat Dec 11 09:49:03 2021 daemon.notice openvpn(OpenWRT)[2454]: /usr/libexec/openvpn-hotplug up OpenWRT tun0 1500 1538 10.26.8.74 255.255.255.0 init
Sat Dec 11 09:49:03 2021 user.notice firewall: Reloading firewall due to ifup of OpenWRT (tun0)
Sat Dec 11 09:49:08 2021 daemon.notice openvpn(OpenWRT)[2454]: net_route_v4_add: 141.98.102.242/32 via 192.168.1.1 dev [NULL] table 0 metric -1
Sat Dec 11 09:49:08 2021 daemon.notice openvpn(OpenWRT)[2454]: net_route_v4_add: 0.0.0.0/1 via 10.26.8.1 dev [NULL] table 0 metric -1
Sat Dec 11 09:49:08 2021 daemon.notice openvpn(OpenWRT)[2454]: net_route_v4_add: 128.0.0.0/1 via 10.26.8.1 dev [NULL] table 0 metric -1
Sat Dec 11 09:49:08 2021 daemon.notice openvpn(OpenWRT)[2454]: Initialization Sequence Completed

[OpenSourcerer 1441]

I'd couple the address with two others and connect them with AND: If address A B C are out, then run the script.
Which doesn't answer your new question about alternative addresses, so you should wait for others to reply.