I need help with two problems?

Problem#1
I am working with a game server, which is built with Unity 5.3.5 with the help of headless mode. This program is running using a simple bash script on a remote server.

I am capable of handling errors using exception handlers or Handle log function (with execution saved in a log file). The function is crashing for last few days, and I can't write anything (as this is the only function available). This script is running in a multi launcher location, with 17410 representing error log file. While trying to access the bash file, it is returning 134 error.

I am confused with this SIGABRT issue. I am looking forward to a simple solution like stacktrace (is there any available??). I can't handle this in the development phase. And non-headless mode is simply not possible (as it misses the OpenGL). Also, I am unable to reproduce the crash, as it only happened once on an Ubuntu machine. I was playing this game for more than an hour.

For now, I am unable to create a log file or make a packet several times, so that I get the program crashing code lines or due to performance issues. (I am not sure if it is just one line or more).

Problem#2:

First, see these chunks code:

Code 1:
using UnityEngine;
Using System.Collections;

public class Class1: MonoBehaviour {

// Plane Vs Viewpoint orientation and using a simple boolean as a flag operator
public bool Orient1 = false;

void Update() {
Vector3 targetlocation;

if (Orient1) {
targetlocation = Camera.main.transform.position;
}
else {
targetlocation = transform.position - Camera.main.transform.forward;
}

// This make sure the movement is around the Y-Axis
targetlocation.y = transform.position.y;
transform.LookAt(targetlocation);
}
}

Code 2:
using UnityEngine;
using System.Collections;

public class ABTSwitcher : MonoBehaviour {

public Texture2D[] simpleT;
private int CTI = 0;
private Vector3 simple_V;

void Awake() {
// This position is the reference vector I am using
simple_V = transform.forward;
}

void Update() {
float Position_Ang = Vector3.Dot(simple_V, (Camera.main.transform.position - transform.position).normalized);
Position_Ang = Mathf.Rad2Deg * Mathf.Acos(Position_Ang);
float increaseT = 360.0f / simpleT.Length;
int differential = (int)(Position_Ang / increaseT);

if (CTI != differential) {
// I am changing the texture with a simple command
GetComponent<Renderer>().material.SetTexture("_MainTex", simpleT[interval]); // I have changed this line
CTI = differential;
}
}
}

These lines of codes are applied to Quad, but the camera is not directly facing/communicating/interfering with the billboard. On changing line from the first script to targetlocation = transform.position - Camera.main.transform.forward; (#13) is giving the another (non-wanted) result. The facing angle is corrected by changing, but it lost the tracking ability. Any help? I am trying to create an AI application, where the camera is seeing the screen and tracking the movement (and learning it, after learning it will play without any external help). After the recording, it will be processed by image processing machine; it will feed the data to an AI algorithm, which will generate different cases. I am perusing with unturned (as it is simple and processing is easy compared to other games) and I am getting the items data from http://unturneditemid.com. This data will reduce the processing time by 1/8 and will help in quick recovery in case of lost in a convergence problem.