I created a map in ArcGIS Pro 2.3.2 with a point feature class that has custom picture markers for its symbols. I then created a vector tile package from this map, and shared it to ArcGIS Online. I then published this in AGO as a tile layer, and added this tile layer to a new web map as the basemap. I saved the web map. The web map appears as expected in AGO map viewer. When I try to open the web map in ArcGIS Explorer on my Android phone I get an error saying "Can't open map Invalid response". I removed the layer that contains the picture marker symbols and went through the whole workflow again. Once I did that, the map was viewable in ArcGIS Explorer.
Has anyone else experienced this behaviour? Does ArcGIS Explorer not support vector tile layers that contain layers with custom picture markers?