My phone just got repaired a second time, after I managed to nail the problem down to the core-module again. I’m waiting for it to come back, then I’ll do tests again.
If you notice the same problem as me, with a kernel wakelock draining the battery, please do a #dic:backup at once! My first core-module litterally died because of this issue.
You can also observe the draining of the battery because of a kernel wakelock through the app BetterBatteryStats (needs root). The link to the xda-thread was given higher in the topic. It’s easier if you don’t want to go through a terminal.
I use BatteryChargeLimit to avoid overcharging, but it doesn’t help for a battery drain, only for the health of the battery.
Btw., I’m actually more or less happy of having had this problem, as this is what made me sign up on the forum