When modeling a microcontroller in microchip studio + proteus and applying a signal to the input ports, the program does not work correctly, what am I doing wrong?

Question

C++ / C#

I’m starting to study MK and modeling atmega8 in proteus, following the example I made a program with 2 buttons, one increases the value on the seven-segment indicator by 1, the second decreases by 1. In this case, everything works, no problems, the values ​​\u200b\u200bincrease / decrease according to the condition. I decided to modernize the program and added 2 more buttons, one increases the value by 2, the second decreases it by 2. I compile the program, load it into the proteus, and when you click on any of the buttons, nothing happens. If you hold down one button and then press another, the value increases or decreases, depending on the button. If you hold down two buttons and click on the other, then the values ​​begin to increase or decrease spontaneously, and the direction of the value change does not correspond to the last button pressed. What am I doing wrong and is it possible to implement similar functionality in this way? and if not, in what direction should we move in order to implement our plans?
I am attaching a link to the program for MK and the scheme in Proteus.
https://pastebin.com/UZPLkm79 code
https://drive.google.com/file/d/1uDOV-kdm_ww_Oo7Lt... scheme in proetus
https://drive.google.com/file/d/19D5w0Ndbah8iq_57M.. .ready project for microchipstudio