I afraid the fixed ratio issue will not solved in the next time, since it is a know problem since a very long time. There is a workaround, but I don't want to post it at the forum, so that the developers are more motivated to fix the issue.
I use a few extra render buttons for Enscape where I use this commands:
-viewportproperties s 1200 600 enter
This are the commands from my 2:1 render button. If always use a button like this you will never have a problem with a wrong output anymore. I have buttons for different ratios.
Thank you so much for the tip! This has been driving me nuts, but they say it is fixed in 2.6 so im looking forward to try that