After i changed in /etc/default/grub these lines: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash vmalloc=256M" GRUB_CMDLINE_LINUX="gfxpayload=1024x768x24,1024x768 splash" the bug did not appear again.
After i changed in /etc/default/grub these lines: LINUX_DEFAULT= "quiet splash vmalloc=256M" LINUX=" gfxpayload= 1024x768x24, 1024x768 splash"
GRUB_CMDLINE_
GRUB_CMDLINE_
the bug did not appear again.