If you get the error message "the gallery not responding", it is usually because a sector of the hard drive is deffective or the format is incorrect.
1. To be sure that your drive is the source of the problem, disconnect all the connected drives. If you do not see the error message, it means that your drive format or allocation tables are incorrects. In this case, please try to format your drive in ExFAT (compatible with Android, Mac and Windows).
2. If you still get the error message without any drive connected, it may be because of an issue with the Firmware.
In this case, you can apply this procedure:
And if the problem still persists, so you can apply this process as last resort :