This is pure speculation,
try moving the
AddTimer("Update", 2.0f, "Update");
above the rest of the code in the Update function.
void Update(string &in asTimer)
{
    AddTimer("Update", 2.0f, "Update");
    playerIsRunning = (GetPlayerSpeed() > 3) ? true : false;
    
    if(playerIsRunning)
    {
        //AddDebugMessage("Current main time divider: "+mainTimeDivider+"", false);
        if(mainTimeDivider == 10){
            //Do nothing 
        }
        else 
        {
            mainTimeDivider++;
        }
    }
    else
    {
        //AddDebugMessage("Current main time divider: "+mainTimeDivider+"", false);
        
        if(mainTimeDivider == 0){ 
            //Do nothing 
        }
        else 
        {
            mainTimeDivider--;
        }
    }
    
    AddDebugMessage("Current main time divider: "+mainTimeDivider+"", false);
}