How to fix weird flickering?

Hello,

I am making a game similar to Flappy Bird, where the player stays in place (only moves up and down), but the obstacles scroll(to the left). I wanted to make a trail for my player, but since the player isn’t actually moving this proved rather difficult. Currently, I am using a Line Renderer that makes the trail.

https://i.sstatic.net/oD8ZCIA4.gif

My code:

using System.Collections.Generic;
using UnityEngine;

public class TrailLine : MonoBehaviour
{
    public LineRenderer line;
    public float minDistance;
    public float scrollSpeed;
    public List<Vector3> lineVertices = new List<Vector3>();

    void Start () {
        lineVertices.Add(transform.position);
        lineVertices.Add(transform.position);
    }

    void Update()
    {
        lineVertices.RemoveAt(lineVertices.Count - 1);

        for (int i = 0; i < (lineVertices.Count); i++) {
            lineVertices[i] = new Vector3(lineVertices[i].x - scrollSpeed * Time.deltaTime, lineVertices[i].y);
        }

        addCurrentPosition();
        line.SetPositions(lineVertices.ToArray());

        
    }

    public void addCurrentPosition() {
        lineVertices.Add(transform.position);
        line.positionCount = lineVertices.Count;
    }

}

The addCurrentPosition method is called whenever the player changes direction, and thus an extra point is added to the line. This works well, however there is some weird “bouncing” that I do not understand.

How can I fix it?

Waiting for more information about it. I hope someone will reply in details.