I have turned SmartReflex off again via "/etc/pmconfig" & rebooted and the device just keeps charging for another hour! Maybe I will try a hard reboot (turn off and on instead of using the reboot via DBUS signal).

The stability issues seem to be related to earlier firmware versions, I am using the latest firmware. Anyway, I have observed no stability problems (well one browser crash, but that may be coincidence), just the weird charging issue.