I see from your post that you are running 8.5.3. I ran into some issues with RTF's in 8.5.3 where you could not add a RTF to a dialog which was fixed in 9.0.x so obviously there were probably other issues as well. 

Are both servers running 8.5.3? In any event, even not considering this issue, you should seriously consider moving to 9.

I think the problem is the "none" installation of xPages modules on the server. There are css missing, the RT fields are not displayed with the ckeditor.

How can I check if all the xPages required files/css/libs/dojo are well installed on the Domino server ?

G,

Well if the 2 servers are not pretty much identical.  That could be the problem.  They should be the same server version, fixpack, hotfix, jvm update etc...  They should also have the same version of the Extension Library if you're running that.    Ideally they should be on the most recent versions because they do put a lot of fixes to bugs in not only the core domino updates and fix packs but also the ext. library from OpenNTF.

I would not worry about checking for individual files/css etc.  I'd focus on the installed versions of everything.  

Also - you said in the other post you're not getting any errors...  but you don't say where you're looking.  Errors could be occuring that don't cause the page to blow up and stack trace.  You should definately have a display errors control on the page if you don't already.  Also you should install the XPages Log file reader on both your servers.  That contains several pages that lets you easily look for errors "behind the scenes".  It's possible that the problem server is giving off errors.

Dave

When I remove the RT fields. The document is saved perfectly well.

When I add a RT field control. The document is in edit mode and stays in edit mode.

What controls the RT controls ? Are there configuration settings needed on server level ? Security permissions ?

I don't have control on the servers, so I can't compare the 2 servers.

I know there is certainly a difference in the config of the servers only based on the basic layout of a test applic

Server A is 8.5.3F3

Server B is 8.5.3F6