Hi,
I'm not familiar with your microcontroller.
You need to reset it after you have determined the previous reset reason.
This means you - with your software - need to clear thos buts after you read them.
Otherwise they may "survive" the next reset and show you wrong reset causes.
--> clear them.
If they still show BOR and POR, then it's definitely a microcontroller power supply problem.
Do you have
* a good PCB layout
* a solid GND plane, not split in pieces
* used decoupling capacitors at every VCC pin
* used decoupling capacitor at the RESET pin
* used a large enough bulk capacitor somewhere at VCC
For more detailed help, you need to provide more detailed informations:
*
2. There is a parameter like current which can be varied externally.
What does this mean? Is it low frequency current, or pulsed current, near the microcontroller, what magnitude?
* show us your schematic
* show us your PCB layout
* show us your code
Klaus