Unreliable DSL (PPP) connection

On Turris OS 4.0.3, I had configured a WAN interface of my MOX classic to PPPoE protocol (behind VDSL modem in bridge mode).

The connection is fine, however it is unreliable after reboot. The connection flaps up and down after reboot and in fact never gets fully connected. If I issue /etc/init.d/network restart manually after reboot, the connection goes up and everything is fine until next reboot.

This issue is really annoying and critical as

1. It needs manual action after each reboot
2. The device is not remotely accessible until someone connects and fix PPP connection from LAN

WAN interface configuration in /etc/config/network (generated from Foris) is:

config interface 'wan'
	option ifname 'eth0'
	option ipv6 '1'
	option proto 'pppoe'
	option username 'adsl'
	option password 'adsl'

First log messages about PPP in /var/log/messages are: ppp-issue_startup.log

Repeating log messages are: ppp-issue_repeating.log