On GeoServer I have two layers, both cascading a remote WMS. Both layers work fine in the layer preview.

Now I am putting both into one group layer and open the preview, which shows an empty response. When trying to query the group layer in the browser with

localhost:8080/geoserver/ws/wms?service=WMS&version=1.1.1&request=GetMap&layers=ws:layername&styles=&bbox=6.03777,48.898,14.703518328104952,54.93599775300893&width=768&height=535&srs=EPSG:4326&format=image/png&

I get the following response:

Rendering process failed Argument "bgColor" should not be null.

When I add bgColor=0xFFFFFF& to the request, I still get the same error response.

The same happens, when I call the underlying layers within the layers parameter, without using the group layer.

I thought, it might be about different WMS implementations on the remote WMS side, but even when I switch to different remote WMS services, the problem persists.

When Googling, I didn't find a response that seems to solve the problem. Do I miss something?

UPDATE

The WMS services I am using are

• http://www.geodaten-mv.de/dienste/adv_dop, layer mv_dop
• https://geodienste.sachsen.de/wms_geosn_dop-rgb/guest, layer sn_dop_020

On GeoServer I have two layers, both cascading a remote WMS. Both layers work fine in the layer preview.

Now I am putting both into one group layer and open the preview, which shows an empty response. When trying to query the group layer in the browser with

localhost:8080/geoserver/ws/wms?service=WMS&version=1.1.1&request=GetMap&layers=ws:layername&styles=&bbox=6.03777,48.898,14.703518328104952,54.93599775300893&width=768&height=535&srs=EPSG:4326&format=image/png&

I get the following response:

Rendering process failed Argument "bgColor" should not be null.

When I add &bgColor=0xFFFFFF to the request, I still get the same error response.

The same happens, when I call the underlying layers within the layers parameter, without using the group layer.

I thought, it might be about different WMS implementations on the remote WMS side, but even when I switch to different remote WMS services, the problem persists.

When Googling, I didn't find a response that seems to solve the problem. Do I miss something?

UPDATE

The WMS services I am using are

• http://www.geodaten-mv.de/dienste/adv_dop, layer mv_dop
• https://geodienste.sachsen.de/wms_geosn_dop-rgb/guest, layer sn_dop_020

On geoserver I have two layers, both cascading a remote WMS. Both layers work fine in the layer preview.

Now I am putting both into one group layer and open the preview, which shows an empty response. When trying to query the group layer in the browser with

localhost:8080/geoserver/ws/wms?service=WMS&version=1.1.1&request=GetMap&layers=ws:layername&styles=&bbox=6.03777,48.898,14.703518328104952,54.93599775300893&width=768&height=535&srs=EPSG:4326&format=image/png

, I get the following response:

Rendering process failed Argument "bgColor" should not be null.

When I add &bgColor=0xFFFFFF to the request, I still get the same error response.

The same happens, when I call the underlying layers within the &layers parameter, without using the group layer.

I thought, it might be about different wms implementations on the remote WMS side, but even when I switch to different remote wms services, the problem persists. When googling, I didn't find a response that seems to solve the problem. Do I miss something?

UPDATE

The WMS services I am using are

• http://www.geodaten-mv.de/dienste/adv_dop, layer mv_dop
• https://geodienste.sachsen.de/wms_geosn_dop-rgb/guest, layer sn_dop_020

On GeoServer I have two layers, both cascading a remote WMS. Both layers work fine in the layer preview.

Now I am putting both into one group layer and open the preview, which shows an empty response. When trying to query the group layer in the browser with

localhost:8080/geoserver/ws/wms?service=WMS&version=1.1.1&request=GetMap&layers=ws:layername&styles=&bbox=6.03777,48.898,14.703518328104952,54.93599775300893&width=768&height=535&srs=EPSG:4326&format=image/png&

I get the following response:

Rendering process failed Argument "bgColor" should not be null.

When I add bgColor=0xFFFFFF& to the request, I still get the same error response.

The same happens, when I call the underlying layers within the layers parameter, without using the group layer.

I thought, it might be about different WMS implementations on the remote WMS side, but even when I switch to different remote WMS services, the problem persists.

When Googling, I didn't find a response that seems to solve the problem. Do I miss something?

UPDATE

The WMS services I am using are

• http://www.geodaten-mv.de/dienste/adv_dop, layer mv_dop
• https://geodienste.sachsen.de/wms_geosn_dop-rgb/guest, layer sn_dop_020

On geoserver I have two layers, both cascading a remote WMS. Both layers work fine in the layer preview.

Now I am putting both into one group layer and open the preview, which shows an empty response. When trying to query the group layer in the browser with

localhost:8080/geoserver/ws/wms?service=WMS&version=1.1.1&request=GetMap&layers=ws:layername&styles=&bbox=6.03777,48.898,14.703518328104952,54.93599775300893&width=768&height=535&srs=EPSG:4326&format=image/png

, I get the following response:

Rendering process failed Argument "bgColor" should not be null.

When I add &bgColor=0xFFFFFF to the request, I still get the same error response.

The same happens, when I call the underlying layers within the &layers parameter, without using the group layer.

I thought, it might be about different wms implementations on the remote WMS side, but even when I switch to different remote wms services, the problem persists. When googling, I didn't find a response that seems to solve the problem. Do I miss something?

On geoserver I have two layers, both cascading a remote WMS. Both layers work fine in the layer preview.

Now I am putting both into one group layer and open the preview, which shows an empty response. When trying to query the group layer in the browser with

localhost:8080/geoserver/ws/wms?service=WMS&version=1.1.1&request=GetMap&layers=ws:layername&styles=&bbox=6.03777,48.898,14.703518328104952,54.93599775300893&width=768&height=535&srs=EPSG:4326&format=image/png

, I get the following response:

Rendering process failed Argument "bgColor" should not be null.

When I add &bgColor=0xFFFFFF to the request, I still get the same error response.

The same happens, when I call the underlying layers within the &layers parameter, without using the group layer.

I thought, it might be about different wms implementations on the remote WMS side, but even when I switch to different remote wms services, the problem persists. When googling, I didn't find a response that seems to solve the problem. Do I miss something?

UPDATE

The WMS services I am using are

• http://www.geodaten-mv.de/dienste/adv_dop, layer mv_dop
• https://geodienste.sachsen.de/wms_geosn_dop-rgb/guest, layer sn_dop_020