Nothing has been done to that unit than some power losses here and there. So, to test out that bug I mis-configured a system watchdog, so it will pretty much constantly (once after ~3 minutes) reboot the unit:
/system watchdog set auto-send-supout=no automatic-supout=no no-ping-delay=2m watch-address=\ 188.8.131.52 watchdog-timer=yes
That is what is being configured into the ppp-client for the GSM modem:
/interface ppp-client add add-default-route=yes allow=chap apn=internet.emt.ee comment=\ "To the GSM..." data-channel=3 dial-command=ATDT \ dial-on-demand=no disabled=no info-channel=3 keepalive-timeout=30 \ max-mru=1500 max-mtu=1500 modem-init="" mrru=disabled name=ppp-out1 \ null-modem=no password="" phone=*99# pin=0000 port=usb2 profile=default \ use-peer-dns=yes user=""
# /interface ppp-client add add-default-route=yes allow=pap,chap,mschap1,mschap2 comment=\ "To the GSM..." data-channel=3 dial-command=ATDT \ dial-on-demand=yes disabled=no info-channel=3 keepalive-timeout=30 max-mru=\ 1500 max-mtu=1500 modem-init="" mrru=disabled name=ppp-out1 null-modem=no \ password="" phone="" pin="" port=usb2 profile=default use-peer-dns=yes \ user=""
I can not say that the system watchdog is causing that configuration erasing, but I recall as not having that issue before I choose to implement that.
I doubt that it has anything to do with the GSM modem brand (it has Option GTM378 in it) and is some sort of long standing bug within the ROS.
How to make the ppp-client configuration not to get changed by mere power cycling the unit?