The RemoveAll() and RemoveAt() methods for the source collection of a MediaLayer displays unexpected behavior by displaying the old image underneath a new image in ArcGIS Maps SDK for JavaScript 4.26.
The RemoveAll() and RemoveAt() methods work and function as designed for the MediaLayer's source property, which is a collection of elements. Refer to https://developers.arcgis.com/javascript/latest/api-reference/esri-layers-MediaLayer.html#source for more information.