ML-Agent "std of reward: 0.000." Agent stops learning

Question

I've been trying to train my self-balancing agent to learn to keep his waist above a certain position. But after a while, he just repeatedly keeps trying the same approach/tactic over and over again. His mean-reward and std-of-reward just stay the same. What's the best way to approach this? Thank you.

Agent Script:

using MLAgents;
using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using MLAgents.Sensor;

public class BalanceAgent : Agent
{
    private BalancingArea area;
    public GameObject waist;
    public GameObject buttR;
    public GameObject buttL;
    public GameObject thighR;
    public GameObject thighL;
    public GameObject legR;
    public GameObject legL;
    public GameObject footR;
    public GameObject footL;

    public GameObject[] bodyParts = new GameObject[9];
    public Vector3[] posStart = new Vector3[9];
    public Vector3[] eulerStart = new Vector3[9];
    public RayPerceptionSensorComponent3D dirForward;

    public void Start() {
        bodyParts = new GameObject[] { waist, buttR, buttL, thighR, thighL, legR, legL, footR, footL };

        for (int i = 0; i < bodyParts.Length; i++) {
            posStart[i] = bodyParts[i].transform.position;
            eulerStart[i] = bodyParts[i].transform.eulerAngles;
        }
    }

    public override void InitializeAgent() {
        base.InitializeAgent();
        area = GetComponentInParent<BalancingArea>();
    }

    public override void AgentReset() {
        for (int i = 0; i < bodyParts.Length; i++) {
            bodyParts[i].transform.position = posStart[i];
            bodyParts[i].transform.eulerAngles = eulerStart[i];
            bodyParts[i].GetComponent<Rigidbody>().velocity = Vector3.zero;
            bodyParts[i].GetComponent<Rigidbody>().angularVelocity = Vector3.zero;
        }
    }

    public override void AgentAction(float[] vectorAction) {

        int buttRDir = 0;
        int buttRVec = (int)vectorAction[0];
        switch (buttRVec) {
            case 3:
                buttRDir = 0;
                break;
            case 1:
                buttRDir = -1;
                break;
            case 2:
                buttRDir = 1;
                break;
        }
        buttR.transform.Rotate(0, buttRDir, 0);

        int buttLDir = 0;
        int buttLVec = (int)vectorAction[1];
        switch (buttLVec) {
            case 3:
                buttLDir = 0;
                break;
            case 1:
                buttLDir = -1;
                break;
            case 2:
                buttLDir = 1;
                break;
        }
        buttL.transform.Rotate(0, buttLDir, 0);

        int thighRDir = 0;
        int thighRVec = (int)vectorAction[2];
        switch (thighRVec) {
            case 3:
                thighRDir = 0;
                break;
            case 1:
                thighRDir = -1;
                break;
            case 2:
                thighRDir = 1;
                break;
        }
        thighR.transform.Rotate(0, thighRDir, 0);

        int thighLDir = 0;
        int thighLVec = (int)vectorAction[3];
        switch (thighLVec) {
            case 3:
                thighLDir = 0;
                break;
            case 1:
                thighLDir = -1;
                break;
            case 2:
                thighLDir = 1;
                break;
        }
        thighL.transform.Rotate(0, thighLDir, 0);

        int legRDir = 0;
        int legRVec = (int)vectorAction[4];
        switch (legRVec) {
            case 3:
                legRDir = 0;
                break;
            case 1:
                legRDir = -1;
                break;
            case 2:
                legRDir = 1;
                break;
        }
        legR.transform.Rotate(0, legRDir, 0);

        int legLDir = 0;
        int legLVec = (int)vectorAction[5];
        switch (legLVec) {
            case 3:
                legLDir = 0;
                break;
            case 1:
                legLDir = -1;
                break;
            case 2:
                legLDir = 1;
                break;
        }
        legL.transform.Rotate(0, legLDir, 0);

        int footRDir = 0;
        int footRVec = (int)vectorAction[6];
        switch (footRVec) {
            case 3:
                footRDir = 0;
                break;
            case 1:
                footRDir = -1;
                break;
            case 2:
                footRDir = 1;
                break;
        }
        footR.transform.Rotate(0, footRDir, 0);

        int footLDir = 0;
        int footLVec = (int)vectorAction[7];
        switch (footLVec) {
            case 3:
                footLDir = 0;
                break;
            case 1:
                footLDir = -1;
                break;
            case 2:
                footLDir = 1;
                break;
        }
        footL.transform.Rotate(0, footLDir, 0);

        //buttR = vectorAction[0]; //Right or none
        //if (buttR == 2) buttR = -1f; //Left

        if (waist.transform.position.y > -1.4f) {
            AddReward(.1f);
        }
        else {
            AddReward(-.02f);
        }

        if (waist.transform.position.y <= -3) {
            Done();
            print("He fell too far...");
        }
    }

    public override void CollectObservations() {

        for(int i = 0; i < bodyParts.Length; i++) {
            AddVectorObs(bodyParts[i].transform.position);
            AddVectorObs(bodyParts[i].transform.eulerAngles);
            AddVectorObs(bodyParts[i].GetComponent<Rigidbody>().velocity);
            AddVectorObs(bodyParts[i].GetComponent<Rigidbody>().angularVelocity);
            //AddVectorObs(dirForward);
        }
    }
}