Photoshop background not properly filling

Question

I am trying to fill background layer with gradient, but its not properly filling. I have attached the screen shot for the same. Also in layer thumbnail it show white lines,
I don't know what happened, it was working fine suddenly it is behaving like this ! Any help ?

Answer 1

I guess it's a bug, Try to reset your preferences.

Goto Edit menu > Preferences > General > Reset Preferences on quit > Restart Photoshop

Method 2

Try updating Photoshop version