diff --git a/css/src/components/ajax-progress.module.css b/css/src/components/ajax-progress.module.css
index 59268d4..8d72ade 100644
--- a/css/src/components/ajax-progress.module.css
+++ b/css/src/components/ajax-progress.module.css
@@ -47,9 +47,6 @@
   border-radius: 50%;
   animation: claro-throbber 0.75s linear infinite;
 }
-[dir="rtl"] .ajax-progress__throbber {
-  animation-direction: reverse;
-}
 
 .ajax-progress__message {
   display: inline-block;
@@ -77,7 +74,7 @@
   box-sizing: border-box;
   z-index: 1000;
 }
-.ajax-progress--fullscreen .ajax-progress__throbber {
+.ajax-progress__throbber--fullscreen {
   position: absolute;
   top: 50%;
   left: 50%;
@@ -90,6 +87,15 @@
 }
 
 @media screen and (-ms-high-contrast: active) {
+  /**
+   * Throbber animation is shaky on Edge RTL on high contrast for border width
+   * less than 4px.
+   */
+  @supports (-ms-ime-align:auto) {
+    [dir="rtl"] .ajax-progress__throbber {
+      border-width: 4px;
+    }
+  }
   .progress__bar {
     background-color: windowText;
   }
diff --git a/js/claro.ajax.es6.js b/js/claro.ajax.es6.js
index 76c8d1f..5a524b1 100644
--- a/js/claro.ajax.es6.js
+++ b/js/claro.ajax.es6.js
@@ -11,7 +11,7 @@
    *   The HTML markup for the throbber.
    */
   Drupal.theme.ajaxProgressIndicatorFullscreen = () =>
-    '<div class="ajax-progress ajax-progress--fullscreen"><div class="ajax-progress__throbber">&nbsp;</div></div>';
+    '<div class="ajax-progress ajax-progress--fullscreen"><div class="ajax-progress__throbber ajax-progress__throbber--fullscreen">&nbsp;</div></div>';
 
   /**
    * Theme override of the ajax progress indicator.
diff --git a/js/claro.ajax.js b/js/claro.ajax.js
index 9fe4573..485d592 100644
--- a/js/claro.ajax.js
+++ b/js/claro.ajax.js
@@ -7,7 +7,7 @@
 
 (function (Drupal) {
   Drupal.theme.ajaxProgressIndicatorFullscreen = function () {
-    return '<div class="ajax-progress ajax-progress--fullscreen"><div class="ajax-progress__throbber">&nbsp;</div></div>';
+    return '<div class="ajax-progress ajax-progress--fullscreen"><div class="ajax-progress__throbber ajax-progress__throbber--fullscreen">&nbsp;</div></div>';
   };
 
   Drupal.theme.ajaxProgressThrobber = function (message) {