Duplicate image on the slide

Well, my <ion-slides> receives images dynamically from a server. But some images overlap the others, the amount in the pagination is correct, and when I give swap on the slide, the image that should appear back, how to solve? Here is the code:

<ion-slides autoplay="4000" loop="true" pager="true" *ngIf="slides.length">
    <ion-slide *ngFor="let slide of slides">
        <img [src]="slide.base64" *ngIf="!slide.link && slide.base64">
        <a [href]="slide.link" *ngIf="slide.link && !slide.anexos_id && slide.base64">
            <img [src]="slide.base64">
        </a>
        <a [href]="slide.link" download *ngIf="slide.link && slide.anexos_id && slide.base64">
            <img [src]="slide.base64">
        </a>
    </ion-slide>
</ion-slides>