I seem to be having no troubles with 1.9.9. Currently reading a commercial epub from University of Chicago Press: nicely formatted, teeny page numbers show up, I like the 7mm "xx% read • Sleep Mode" notice at the top of the screen. I leave wifi on, auto-sleep in 15 min, power off never.
I was surprised to see the device "sleeping" with the wrong book cover. A bug? Nope: I had put the Kobo Touch aside on the Home screen and put my glasses on top before turning out the light. I triggered the opening of the second book which, 15 minutes later, fell into auto-sleep.