PrimeNG sidebar clears primeng messages. Why?

In my app.component.html I have

<div class="main">
<button type="button" (click)="onShowNotificationSideBar()" label="Show"></button>
<p-sidebar [(visible)]="notificationSideBarVisible" position="right" [style]="{width:'50em'}">
<button type="button" pButton pRipple (click)="showSuccess()" label="S" class="p-button-success"></button>
<button type="button" pButton pRipple (click)="showWarn()" label="W" class="p-button-warning"></button>
<button type="button" pButton pRipple (click)="showError()" label="E" class="p-button-danger"></button>
<h3>Messages</h3>
<h5>{{messages}}</h5>
<p-messages [(value)]="messages" [enableService]="false" ></p-messages>
</p-sidebar>
<p-toast position="center"></p-toast>
<router-outlet></router-outlet>
</div>


in app.component.ts I have

import { Component } from '@angular/core';
import { Message, MessageService } from 'primeng/api';

@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.scss'],
providers: [MessageService]
})
export class AppComponent {
title = 'WECO';
notificationSideBarVisible = false;

constructor(private messageService: MessageService) {
messageService.messageObserver.subscribe((m:Message | Message[])=>{
if (!Array.isArray(m)){
this.messages.push(m)
}
this.messages = [...this.messages];
});
}

onShowNotificationSideBar(){
this.notificationSideBarVisible=true;
}

count=0;

messages : Message[] = [
// { severity: 'success', summary: 'Success', detail: 'Message Content' },
// { severity: 'info', summary: 'Info', detail: 'Message Content' },
// { severity: 'warn', summary: 'Warning', detail: 'Message Content' },
// { severity: 'error', summary: 'Error', detail: 'Message Content' }
];

longSentence = 'Let’s end all this nonsense about how long sentences = run-on sentences. You can have a six-word run-on sentence (“I went shopping I ate donuts.”), while most of the sentences below are much, much longer than that and are not run-ons';//'And let’s end all this nonsense about how long sentences = run-on sentences. You can have a six-word run-on sentence (“I went shopping I ate donuts.”), while most of the sentences below are much, much longer than that and are not run-ons (except for a few examples like Jose Saramago). But whether the sentence is grammatically correct isn’t nearly as important as whether the sentence is fun or beautiful.'

showWarn(){
let detail='User Deleted a Weco Rule';
if (this.count++%5===0)
detail = this.longSentence;
this.messageService.add({severity:'warn', summary:'User Action', detail: detail});
}

showSuccess(){
let detail = 'Weco Rule 123 Saved';
if (this.count++%5===0)
detail = this.longSentence;
this.messageService.add({severity:'success', summary:'Service Call', detail:detail});
}

showError(){
let detail = 'api-call:get-factories returned 404';
if (this.count++%5===0)
detail = this.longSentence;
this.messageService.add({severity:'error', summary:'Service Call', detail:detail});
}
}


If I open side bar and add some messages in it they appear, but when I close and reopen they are gone. Even though I can see that messages variable still has them. Why?
P.S. If I then add some more messages I only see the new ones.

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