Poor rendering / quality of objects in the viewer

Hi,

I have created a new site in Geocortex Essentials and I reference a web map from ArcGIS Online.

I created a viewer and launched it in my browser to check the rendering. I have all the elements of my map displayed however the quality / rendering of the objects is very bad, their aspects are not clear. While the map and the objects are displayed perfectly in ArcGIS Online.

Do you have any suggestions for improvement?

Thank you!