LG washing machines displaying error code SE are indicating a “motor fault” although the technical information also says it could be a main PCB fault. They recommend to, “try the motor first”.
Like many error codes it’s vague and not too helpful, especially for a DIY repairer. So you really need an engineer to try and sort this one. You can’t possibly justify “trying the motor first” if you interpret that as buying and fitting a new motor. They are way too expensive to gamble on. You need to at least know how to test a motor for faults and check its connections and carbon brushes (if fitted) if you want to try and diagnose the cause. I have some general advice on troubleshooting washing machine motor not running but an engineer would be best.
Find appliance repairs – Book washing machine (or other appliance) repair