This seems to be a common problem with screens. There are threads about it in the Sony forum as well
https://www.mobileread.com/forums/sho...d.php?t=114190
https://www.mobileread.com/forums/sho...=broken+screen
in the Kindle forum
https://www.mobileread.com/forums/sho...=broken+screen
I am sure there are more threads on this issue, but am to lazy to find them now.