I reformulate an unanswered question. In order to put in evidence a problem, I reinstalled the RUT955 firmware without keeping the settings. Now there is no custom scripts.
To highlight the problem:
In system > user scripts, simulate a script by writing:
/usr/bin/logger "hello world"
The wiki says: "The custom commands are executed once the system init finished."
Reboot the RUT955 and analyse the logread.
We see the message "Hello world" and, after 10 seconds, we see the message:
... Digital relay output off
The custom scripts are started BEFORE the end of the init which could not be normal !
In my case a script (launched by rc.local) set the digital relay on and, just after, a process set the relay off which is inconvenient, isn't it ?
Log at your disposal but you can easily check as me.
PS: Jerome knows the problem