Routerboard stops responding until serial input

Hi,

Have an RB433c here. It’s running 4.10 and got a mostly stock config, with the following changes:

/interface pppoe-client
  add ac-name="" add-default-route=no allow=pap,chap,mschap1,mschap2 comment="" dial-on-demand=no disabled=no interface=ether2 max-mru=1480 max-mtu=1480 \
    mrru=disabled name=pppoe-out2 password=XXXXXXX profile=default service-name=OCN use-peer-dns=no user=XXXXXXX@one.ocn.ne.jp
/ip service disable telnet
/ip service disable ftp
/ip service disable www
/ip service disable www-ssl
/ip service disable winbox
/ip address add address=XXX.XXX.XXX.190 interface=ether1 netmask=255.255.255.248

The pppoe client isn’t going to connect just now, as the router hasn’t been shipped to it’s intended destination yet

The device is working, but stops responding to pings at some points. This seems to possibly be periodic. Connecting the serial console shows

  Mikrotik Login: ...

As soon as the admin user logs in, the router starts responding to pings again.

This seems somewhat strange. If it was a network issue, I can’t see how it would coincide with the serial console login. Could this be a hardware / OS fault? Or is there something else which should be checked here.

Regards,
Kevin

Add console cable and wait for the output, which is shown during the described problems (when connection is lost the device).