If you get the error message "the gallery not responding", it is because a sector of the hard drive is deffective. In this case, please try to restore your hard drive using a dedicated software on your computeur. If you still have this message, please try to test with another hard drive to know if this problem comes from your hard drive.
But it may be because of an issue with the Firmware.
In this case, you can apply this article :
And if the problem still persists, so you can apply this process as last resort :