There are two ways that the RLY8-XA module can be used: as an Adicon expansion module, or as a standalone X-10 module. The documentation sheet for the module shows that it has a watchdog timer parameter that can be used to turn off the relays after a given number of seconds if the Adicon bus communications are lost. This can be used as a precaution for applications such as sprinklers where having a relay staying on due to a hardware failure could have bad consequences.
Although the datasheet does not say so, there is also a watchdog timer option in X-10 mode. Here is how its operation can be modified or disabled:
If you look at your LEDs on the RLY8-XA, you should see the COMMS LED flashing 4 times. Each flash represents 15 minutes. You can set the watch dog to 15, 30, 45, 60 and 0 (disabled) minutes by setting the number of flashes to 1,2,3,4 or 0 flashes respectively.
Take the top off the RLY8-XA. There is a white button. Press and release the button until the COMMS LED blinks the desired number of flashes or no longer flashes. No flashes means that the watch dog on the RLY8-XA is disabled (relays will not turn off unless an actual Off command is sent).