I cannot find anywhere in the OGC WMS specification that a layer name attribute shall be unique, which is strange to me.
For example if you have a look at the below WMS service
https://www.gebco.net/data_and_products/gebco_web_services/web_map_service/mapserv?service=WMS&version=1.3.0&request=GetCapabilities
the layers' names are not unique and the service is still working fine in QGIS.
It's obviously good practice to use unique layer names when building a WMS service, however I don't understand why the specification is not more restrictive about that, and how QGIS identifies one layer from another with the same name?
<eastBoundLongitude>360</eastBoundLongitude>
values are wrong in the GetCapabilities response (value can't be higher than +180)