Sami - It still seems like your problem is the MCU restarting over and over again as power is going down. As Andy has said you need to carefully evaluate what your reset and VCC decay are doing as the system is shut down. The outputs you see on the terminal screen sure seem to indicate that your program is simply starting over multiple times.

Some MCUs have a detector circuit that checks for missing clocks on the crystal oscillator and will reset the device internally if the clock shows a failure. Maybe your case is that the MCU supports this feature and your oscillator is making hickups while power begins to drop.

Michael Karas