The only other thing I can recommend is installing .NET 4.6, or try launching the game as an administrator. You may have to do this from the games exe file itself (right click properties, check run as administrator). So forth and so on... It's a pretty old game and since this is a private server, we don't have Mythic/WarhammerOnline Company and such to help us debug client problems. It's all community based here.
One of the major issues here is that, people are not putting their system specs/information to help solve the issue. What graphics card are you using? What Operating System? Windows/Linux/MacOS, etc.. How much memory do you have and such. You know basic information folks need to fix issues. The other problem is that when folks tend to fix things, they almost never come back to the forums and say how they fixed it or if they fixed it. So you'll find a lot of incomplete threads were it seems they somehow fixed it but never bothered to respond to the thread on how they fixed it.
I'm sorry it hasn't worked for you. I don't know what else to add here. This issue has been discussed in the past if you do a search on the forums but nobody has found the exact cause or fix. It does seem to be isolated to certain systems.
I mean there are quite a number of threads on the issue or related to it.
https://returnofreckoning.com/forum/vie ... hp?t=15095
viewtopic.php?t=24303
viewtopic.php?f=4&t=16&start=1020#p395123
https://returnofreckoning.com/forum/vie ... hp?t=14523
viewtopic.php?f=4&t=4641
viewtopic.php?t=3061
viewtopic.php?f=4&t=20349
viewtopic.php?f=4&t=35897
viewtopic.php?t=20319
viewtopic.php?t=22783