MCU reset itself

Hello there,

I have wroted my code a while ago. And I need to modify it and add some variable.

So, when I add it, the MCU get reset while working. In my opinion, some rom/ram area overwrited.

I am not much experienced, so could not find solution. Adding some picture below. If I add this two 16-bit variable, the mcu get reset.

Thank you for your help.