Why do images and animations disappear when adding a class to the last column?

Question

I'm trying to animate 6 images in an infinite loop.

When I add the 6th image and add the "poster" class, no image displays, but if I omit adding the "poster" class to the 6th column (or image), the first 5 images display correctly and animation.

I don't understand why this happens.

As you can see, the "poster" class is not in the sixth column, so my code works, but as soon as I add that class, it stops working.

(I'm using bootstrap 5 but I'm sure this has nothing to do with this issue as the code as I show it replicates the issue perfectly)

@keyframes moves {
  to {
    background-position: -100vw 80%;
  }
}

.galeria {
  position: relative;
  overflow: hidden;
}

.poster {
  position: absolute;
  animation: moveAcross 6s linear infinite;
}
.poster-1 {
  animation-delay: -0s;
  animation-duration: 6s;
}
.poster-2 {
  animation-delay: -1s;
  animation-duration: 6s;
}
.poster-3 {
  animation-delay: -2s;
  animation-duration: 6s;
}
.poster-4 {
  animation-delay: -3s;
  animation-duration: 6s;
}
.poster-5 {
  animation-delay: -4s;
  animation-duration: 6s;
}
.poster-6 {
  animation-delay: -5s;
  animation-duration: 6s;
}

@keyframes moveAcross {
  0% {
    left: -300px;
  }
  100% {
    left: 110%;
  }
}

<div class="row justify-content-center">
    <div class="galeria">
        <div class="col poster poster-1">
            <img src="images/posters/poster1.jpg" class="img-fluid" />
        </div>
        <div class="col poster poster-2 ">
            <img src="images/posters/poster2.jpg" class="img-fluid" />
        </div>
        <div class="col poster poster-3">
            <img src="images/posters/poster3.jpg" class="img-fluid" />
        </div>
        <div class="col poster poster-4 ">
            <img src="images/posters/poster4.jpg" class="img-fluid" />
        </div>
        <div class="col poster poster-5">
            <img src="images/posters/poster5.jpg" class="img-fluid" />
        </div>
        <div class="col poster-6">
            <img src="images/posters/poster6.jpg" class="img-fluid" />
        </div>
    </div>
</div>

Answer 1

In the sixth column, it works perfectly with class .poster, whether using Bootstrap 5 or not.

edit: You can add a poster with a hidden attribute at the end and it will work as long as the last poster does not contain class .poster :)

<div style="visibility: hidden;">
    <img src="https://soft.com.mx/test/images/posters/poster6.jpg" class="img-fluid" />
</div>

@keyframes moves {
to {
    background-position: -100vw 80%;
}
}

.galería {
position: relative;
overflow: hidden;
}

.poster {
position: absolute;
animation: moveAcross 6s linear infinite;
}
.poster-1 {
animation-delay: -0s;
animation-duration: 6s;
}
.poster-2 {
animation-delay: -1s;
animation-duration: 6s;
}
.poster-3 {
animation-delay: -2s;
animation-duration: 6s;
}
.poster-4 {
animation-delay: -3s;
animation-duration: 6s;
}
.poster-5 {
animation-delay: -4s;
animation-duration: 6s;
}
.poster-6 {
animation-delay: -5s;
animation-duration: 6s;
}

@keyframes moveAcross {
0% {
    left: -300px;
}
100% {
    left: 110%;
}
}

<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-EVSTQN3/azprG1Anm3QDgpJLIm9Nao0Yz1ztcQTwFspd3yD65VohhpuuCOmLASjC" crossorigin="anonymous">

<div class="row justify-content-center">
    <div class="galeria">
        <div class="col poster poster-1">
            <img src="https://picsum.photos/300/300?random=1" class="img-fluid" />
        </div>
        <div class="col poster poster-2 ">
            <img src="https://picsum.photos/300/300?random=2" class="img-fluid" />
        </div>
        <div class="col poster poster-3">
            <img src="https://picsum.photos/300/300?random=3" class="img-fluid" />
        </div>
        <div class="col poster poster-4 ">
            <img src="https://picsum.photos/300/300?random=4" class="img-fluid" />
        </div>
        <div class="col poster poster-5">
            <img src="https://picsum.photos/300/300?random=5" class="img-fluid" />
        </div>
        <div class="col poster poster-6">
            <img src="https://picsum.photos/300/300?random=6" class="img-fluid" />
        </div>
    </div>
</div>