hi i contacted lg they got me answer here there reply
As for the issue regarding the power, I’m afraid we may have to perform a complete Factory Reset on the device. This especially helps if the issue is caused by software glitches. Before doing this though, please make sure that a backup of all your data (you may use any backup method or application of your choice) has been created already as the factory reset will erase all user information and data that is stored in your phone’s memory and will restore original factory settings. Once ready to reset, just go to your Phone Settings. Navigate to Backup and Reset and then select Factory Data Reset.
you can contact them
call them at 800-793-8896