Tried using same RUT240 firmware version, which you are currently using (RUT2XX_R_00.01.04.1) and "MIB Browser" SNMP application and everything is working without any issue.
I.e., router's configuration:
"MIB Browser's" configuration:
SNMP Walk correctly returns all IODs values:
Could you let me know more details how your "SNMP Server" is connected to the router? Since their IPs are from different networks, does that mean that your "SNMP Server" (192.168.1.4) is connected to RUT240 "remotely" (via WAN interface)?
Do you have an option to reset your RUT240 to factory default settings, enable SNMP once again, then connect your "SNMP Server" directly to router's LAN and try to get information from the router this way? Does this allow you to read information from the router? If no, have you tried using different SNMP applications (it might help to determine if it is router's or application's issue).