Bug Fix: The Scss structure was wrong.

src/sass/core/object/main/_main.scss

@@ -1,12 +1,9 @@
 .splide {
   $root: &;
-
   position: relative;
   visibility: hidden;
 
   &__track {
-    //position: relative;
-    //z-index: 0;
     overflow: hidden;
   }
 

src/sass/core/object/modifiers/_modifiers.scss

@@ -1,47 +0,0 @@
-.splide {
-  $root: &;
-
-  &--rtl {
-    direction: rtl;
-  }
-
-  &--ttb {
-    > #{$root}__track {
-      > #{$root}__list {
-        display: block;
-      }
-    }
-  }
-
-  &--draggable {
-    > #{$root}__track {
-      > #{$root}__list {
-        > #{$root}__slide {
-          user-select: none;
-        }
-      }
-    }
-  }
-
-  &--fade {
-    > #{$root}__track {
-      > #{$root}__list {
-        display: block;
-
-        > #{$root}__slide {
-          position: absolute;
-          top: 0;
-          left: 0;
-          z-index: 0;
-          opacity: 0;
-
-          &.is-active {
-            position: relative;
-            z-index: 1;
-            opacity: 1;
-          }
-        }
-      }
-    }
-  }
-}

src/sass/themes/default/object/main/_main.scss

@@ -43,6 +43,7 @@
 
   &__pagination {
     position: absolute;
+    z-index: 1;
     bottom: .5em;
     left: 50%;
     transform: translateX( -50% );

src/sass/themes/default/object/modifiers/_modifiers.scss

@@ -1,56 +0,0 @@
-.splide {
-  $root: &;
-
-  &--ttb {
-    > #{$root}__track > #{$root}__arrows, > #{$root}__arrows {
-      #{$root}__arrow {
-        left: 50%;
-        transform: translate( -50%, 0 );
-
-        &--prev {
-          top: 1em;
-
-          svg {
-            transform: rotateZ( -90deg );
-          }
-        }
-
-        &--next {
-          top: auto;
-          bottom: 1em;
-
-          svg {
-            transform: rotateZ( 90deg );
-          }
-        }
-      }
-    }
-
-    > #{$root}__pagination {
-      display: flex;
-      flex-direction: column;
-      bottom: 50%;
-      left: auto;
-      right: .5em;
-      transform: translate( 0, 50% );
-    }
-  }
-
-  &--nav {
-    > #{$root}__track {
-      > #{$root}__list {
-        > #{$root}__slide {
-          border: 3px solid transparent;
-
-          &.is-active {
-            border-color: black;
-          }
-
-          &:focus {
-            outline: none;
-          }
-        }
-      }
-    }
-  }
-}

src/sass/themes/default/object/modifiers/_nav.scss

@@ -1,38 +1,21 @@
 .splide {
   $root: &;
 
-  &--ttb {
-    > #{$root}__track > #{$root}__arrows, > #{$root}__arrows {
-      #{$root}__arrow {
-        left: 50%;
-        transform: translate( -50%, 0 );
+  &--nav {
+    > #{$root}__track {
+      > #{$root}__list {
+        > #{$root}__slide {
+          border: 3px solid transparent;
 
-        &--prev {
-          top: 1em;
-
-          svg {
-            transform: rotateZ( -90deg );
+          &.is-active {
+            border-color: black;
           }
-        }
-
-        &--next {
-          top: auto;
-          bottom: 1em;
 
-          svg {
-            transform: rotateZ( 90deg );
+          &:focus {
+            outline: none;
           }
         }
       }
     }
-
-    > #{$root}__pagination {
-      display: flex;
-      flex-direction: column;
-      bottom: 50%;
-      left: auto;
-      right: .5em;
-      transform: translate( 0, 50% );
-    }
   }
 }