Cascading WMS - Is there specific requirements for the cascading service?

I have been trying to set up a cascading WMS service on my 2.26.0 version.
Its an open service, not basic auth required.
The behaviour of GS is not consistent when trying to add WMS Cascading resourse. For the most time when i try to save my WMS the spinner is just spinning after pressing save and never leaves the page for the store configuration of the resourse.Meanwhile GS i unresponsive for about 30+ seconds.
But for the most time the resourse is saved regardless, 2 out of 3 times.
When to publish a layer, chosing “add layer from” from the just saved resource it takes a long time before the list of layers are presented - a lot of the time they are not at all.
After several attempt I finally got the list of layers and selected the one i wanted to publish. After pressing save I got another error.

  • Failed to upgrade lock from read to write state, please re-try the configuration operation

Yesterday I managed to publish a resource successfully, but i realized I saved it under the wrong workspace. I was unable to change the workspace of the the store (spinner never ended, lock issue, server busy or other issues came up), so i had to delete it and start over again.
Now the problems to save and publish a resource has come up. It appear that is a specific WMS that cause most issues. So i wonder if there is any requirement of the WMS that is not be ideal. The resource is from MapServer, national basemap.
I dont know if there is a bug with GS itself, some issues with my instance or the WMS resource is not fit as a cascading wms?
https://wms.geonorge.no/skwms1/wms.norges_grunnkart_graatone?request=GetCapabilities&service=WMS

Hi Kristian,

I just had a quick look to your remote WMS capability and I didn’t see anything wrong.

Problems can occur if the capability request takes too long to reply (not your case) or contains too much things (SRS and/or layers).

Another problem I got recently is a reference to a SRS which was unknown to GeoServer.

Wondering if the XML parsing gets stuck on that invalid schema reference:

https://wms.geonorge.no:80/cgi-bin/norges_grunnkart_graatone?service=WMS&version=1.3.0&request=GetSchemaExtension

This URL won’t work on SSL as intended, nor it will work if one moves it to http.
May not be it, but it’s a possibility.

Cheers
Andrea