Picture marker symbols in the feature layer are unable to display with WebGL enabled when the imageData parameter of the symbol stored at REST Endpoint is long.
This issue is no longer reproducible using ArcGIS API for JavaScript 4.9.
解决办法
Option 1: Disable WebGL in the script.Option 2: Use the picture marker symbols that are smaller in pixel dimension. Shorten the value for imageData, such as 120px x 120px.