C04 indicates a disruption of the spin cycle or an associated phase in the documented Hitachi models. An excessive, insufficient, or shifted load and the machine’s support are checks to make before mechanical diagnosis.
The official Hitachi chart points you to review those conditions. The code does not prove that the motor has failed.
Check how the laundry ended up
With the drum stopped and the lid released, untangle any twisted garments and redistribute the weight. A small load of heavy items can end up concentrated in one area; an overloaded load may not have room to spread out. Adjust the amount and cycle according to the manual, without adding more clothes as an automatic fix.
If the unit rocks on its supports while it is idle, check the installation. Do not try to override the protection by increasing the speed.
If C04 repeats with different loads that are well distributed and with stable support, request a technical inspection. Note the noises and when it stops, but do not force the failure again to record it if there are heavy impacts or movement.
Distinguish an episode tied to a specific load from a repeated stoppage under normal use when requesting service.