Outdated firmware can cause intermittent communication "handshake" failures between the main engine and peripheral trays. Check your current firmware version in the Status Page
: Attempting to replace the main board yourself may require entering service mode to match serial numbers and calibrate the device—this is not a simple plug-and-play swap. Kyocera Printer E7 Error
Sometimes the error is a temporary logic lockup. Kyocera Printer E7 Error