i Had the same problem, i spend a lot of time trying to fix it, but in the end i chose to use the "downgrade" method so the system thinks it is running 6.0 but it was running 6.2, i did that so o got the possibility to reset all setting but keeping my data, and now, after a entire weekend it is golden once more.. now it runs as i should.
if you have the time..... reset or as they say "downgrade".
- i made this account just to write this to you xD
MJ