Strange "Binding overwriting" in logs

I'm looking for a reason for freezes of the system. Just before the freeze I've got such lines in the logs:

cен 06 09:03:31 keddad-pc org.gnome.Shell.desktop[1896]: Window manager warning: Overwriting existing binding of keysym 32 with keysym 32 (keycode b).
сен 06 09:03:31 keddad-pc org.gnome.Shell.desktop[1896]: Window manager warning: Overwriting existing binding of keysym 37 with keysym 37 (keycode 10).
сен 06 09:03:31 keddad-pc org.gnome.Shell.desktop[1896]: Window manager warning: Overwriting existing binding of keysym 39 with keysym 39 (keycode 12).
сен 06 09:03:31 keddad-pc org.gnome.Shell.desktop[1896]: Window manager warning: Overwriting existing binding of keysym 33 with keysym 33 (keycode c).
сен 06 09:03:31 keddad-pc org.gnome.Shell.desktop[1896]: Window manager warning: Overwriting existing binding of keysym 31 with keysym 31 (keycode a).
сен 06 09:03:31 keddad-pc org.gnome.Shell.desktop[1896]: Window manager warning: Overwriting existing binding of keysym 38 with keysym 38 (keycode 11).
сен 06 09:03:31 keddad-pc org.gnome.Shell.desktop[1896]: Window manager warning: Overwriting existing binding of keysym 36 with keysym 36 (keycode f).
сен 06 09:03:31 keddad-pc org.gnome.Shell.desktop[1896]: Window manager warning: Overwriting existing binding of keysym 35 with keysym 35 (keycode e).
сен 06 09:03:31 keddad-pc org.gnome.Shell.desktop[1896]: Window manager warning: Overwriting existing binding of keysym 34 with keysym 34 (keycode d).

What are these? What kind of binding does it overwrite and why? Can it cause be the reason for freezes? UPD: These things appear to happen after each boot