Then I tried the CalculiX version from @prool: CalculiX 2.20 for Win64
I tried it with steady state dynamics up to 100.000 nodes and I got the results every time I tried it. It has some problems with PrePoMax, so I had to add compatibility mode to get it to work but running it from command line works fine. The results can also be read without a problem.
Now I am wondering what is the actual difference between the official CalculiX version and the version compiled by @prool.