Hard-cover issue ==> beware !!
Guys, a few weeks ago I reported some issues with the Kobo becoming touch-unsensitive when left alone for lets say > 30 minutes in sleep mode. Thinking this was a hardware issue, I returned it to the shop and got a new one .. first I thought all was OK, but then when putting the device in the 'hard-cover' I bought, the issue popped up again.
I finally discovered that when closing the cover, there was an 'inside-pocket' in the cover that constantly touched the screen when the cover was closed. This somehow caused the issue as when I just 'cut-out' this pocket (so that the screen isn't touched when the cover is closed) the problem went away.
This was repeatable behavior as also the Kobo I bought for my sister-in-law had exactly the same issue (with the same resolution of cutting-out the pocket of the hard-cover).\
Thought I wanted to let you guys know as this was a 'hard-to-find' issue (and also 'hard-to-explain' as one would expect that in sleep-mode, the touch-screen would be completely insensitive but apparently constant-touches still trigger some software-activity rendering the device insensitive after a prolongued time.
PS> thanks also for replying to my 'margin-questions', using Calibre to convert epubs w.r.t. setting 'no-margins' and filtering existing margin/font settings works excellent and now all epubs behave alike w.r.t. initial font-sizes and responsiveness to margin/font commands by the touch itself rather than relying on the 'baked-in' settings in the epub.