We have an app that we migrated from arcgis 3.x to arcgis 4.21. The problem now is when using a web tile from a specific domain, for example: (https://tileserver.4umaps.com/5/9/11.png) returns a cors policy error. Using the 3.x, it's working but using the newer version, it doesn't work. I tried using different techniques, i.e: adding the url to esriConfig.request.trustedServers, adding an interceptor to the request by adding a "Access-Control-Allow-Origin":"*", still it does not work. All other web tiles work except for this one.
I can show you an example of what the error looks like.
Any help would be really appreciated.
note: I haven't used a proxy yet because this was working before without proxy, I don't want to use it unless there is no other way.