OpenVPN client reconnecting due to --ping-restart even if traffic is flowing both ways
Solution 1:
You know what helps? Not running two openvpn client processes on the client machine at the same time. The first one would reconnect, and at that point the server forgets about the second one and stops pinging it, so the second one eventually reconnects, and so on...
I feel a bit silly now, but I'm leaving this up in case someone else is being similarly silly.