pinball flipper bug

hey. i want to create a simple pinball flipper arm which rotates 45° forward when i hold down space and snaps back zu 0° when i release space. i thought it would work like that:

 using UnityEngine;
 using System.Collections;
 
 public class RotateDegrees : MonoBehaviour {
     [SerializeField] protected Vector3 m_from = new Vector3(0.0F, 45.0F, 0.0F);
     [SerializeField] protected Vector3 m_to = new Vector3(0.0F, -45.0F, 0.0F);
     [SerializeField] protected Vector3 m_neutral = new Vector3(0.0F, 0.0F, 0.0F);
     [SerializeField] protected float m_frequency = 5.0F;
 
     void Update() {
         if (Input.GetKeyDown("space")){
             Quaternion from = Quaternion.Euler(this.m_neutral);
             Quaternion to = Quaternion.Euler(this.m_to);
 
             float lerp = 0.5F * (1.0F + Mathf.Sin(Mathf.PI * Time.realtimeSinceStartup * this.m_frequency));
             this.transform.localRotation = Quaternion.Lerp(from, to, lerp);
         }
         else if (Input.GetKeyUp("space")){
             Quaternion fromsn = Quaternion.Euler(this.m_to);
             Quaternion tosn = Quaternion.Euler(this.m_neutral);
 
             float lerp = 0.5F * (1.0F + Mathf.Sin(Mathf.PI * Time.realtimeSinceStartup * this.m_frequency));
             this.transform.localRotation = Quaternion.Lerp(fromsn, tosn, lerp);
             //Quaternion from = Quaternion.Euler(this.transform.rotation.eulerAngles);
         }
 
         }
 
 }

but that turns out to look like this: https://gfycat.com/ExcellentSourGiraffe

the gif got capured with 30FPS. but its so not working