#U4-5385 fixed Due in version: 7.2.0

src/Umbraco.Core/Media/ImageHelper.cs

@@ -165,6 +165,16 @@ namespace Umbraco.Core.Media
                     ep.Param[0] = new EncoderParameter(Encoder.Quality, 90L);
 
                     // Save the new image using the dimensions of the image
+                    var predictableThumbnailName = thumbnailFileName.Replace("UMBRACOSYSTHUMBNAIL", maxWidthHeight.ToString(CultureInfo.InvariantCulture));
+                    using (var ms = new MemoryStream())
+                    {
+                        bp.Save(ms, codec, ep);
+                        ms.Seek(0, 0);
+
+                        fs.AddFile(predictableThumbnailName, ms);
+                    }
+
+                    // TODO: Remove this, this is ONLY here for backwards compatibility but it is essentially completely unusable see U4-5385
                     var newFileName = thumbnailFileName.Replace("UMBRACOSYSTHUMBNAIL", string.Format("{0}x{1}", widthTh, heightTh));
                     using (var ms = new MemoryStream())
                     {