The battery is an original Nokia one ordered via eBay.
The only possible hardware fauly might be the MMC1 card which is a 3rd party Micro SD card in a Mini adapter. Can that be qa problem ?
In earlier posts I read that the spontaneous reboots were because of a firmware bug which triggers the watchdog inadvertently. And with the better handling of events / watchdog in your improved kernel I hoped this problem would be solved. Now this is not the case then it can be a hardware problem.