This sort of configuration error usually shows up during initial configuration of a 1747-ASB based I/O chassis.
Since you've read the user manual you've seen that the error code d42 indicates that the I/O image size is larger than two logical "Racks", and that the I/O image size is configured by DIP switches on the module, specifically DIP switches 2-5,6,7,8.
For the PLCTalk community to assist you, you must post a description of the modules in the I/O chassis, slot-by-slot (part numbers, preferably) and the DIP switch settings of all the switches on the 1747-ASB adapter module.
It would also be helpful to know more about the SLC-500 system and the I/O network in general, including details about the other RIO adapters on the network and maybe some background information about how long the system has been running, or if any of the modules or devices in the system have recently been modified or replaced.