Hi there,
Just some data points for the kobo team and anyone else having this issue (based on my experience with the kobo - purchased 1 week ago):
-If you try to put the device to sleep from "sideloaded" epubs by using the power button while reading the epub, the device will always power off instead of go to sleep.
-If you go back to the home screen and try to sleep with the power button, it will sometimes go to sleep and sometimes power off.
-If you let the device idle for 15 minutes while open on a page from a "sideloaded" epub, the device will always go to sleep (at least so far
<- seems a good work-around for now
-If the device previously powered off, when you start reading the epub again, the previous display settings are not remembered i.e. font goes back to default, etc
-If the device previously slept, when you wake it up, the display settings are properly remembered
Liking the customer service so far, based on responses from the dev/support team here...keep up the good work, kobo