Ouch, I feared something like that.
Even worse is that it is not a constant drift but drifts with temperature, that means I cannot simply apply a static correction factor to setwakeup.sh.
Too bad, I was just happy that I found a simple, cheap and powerful dvr solution.
Do you have any gutt feeling how big the temperature drift is? Maybe it's still possible to put a rough correction.
Anyway, I will put my comment on the above mentioned issue and maybe it will be solved someday.
Thanks for your quick response.