X server crashes, why?

Question

Gnome

Suddenly the X's started to drop. They can fall at any time while using the system. Mostly they crash when dialog boxes appear. For example, in chrome, when you try to upload a photo to VK, the X's fall and throws it on the login screen.
I noticed that after the first fall, all gnome extensions were disabled.
On the system -
Asus n53sv, Ubuntu 15.04 Gnome.
.xsessions-error was initially absent, although the path to the file is registered in the /etc/X11/Xsession config.
In along the way ./cache/gdm/session.log saw the following lines

/etc/gdm/Xsession: Beginning session setup...
localuser:dmitry being added to access control list
localuser:dmitry being added to access control list
openConnection: connect: No such file or directory
cannot connect to brltty at :0

What is the problem, how to solve?
And one more question, is it worth switching from X to Wayland?

Answer 1

Ubuntu 15.04 is just the same transitional period from X to Wayland, most likely this is why they fall.
dig in that direction ..
look at what kernel you have, it has been updated from 15.04 or already up to 15.10, try to boot on your native kernel, see if it will fall ...