Whenever I try to enter Tiefhusen in the fixed version of RoA2 the game displays "Drücken Sie Strg+F4 um zu weitergehen" with the only available option being "Weiter". Choosing "Weiter" will simply cause the message to come up again.
I have the same problem in Tiefhusen: pressing ctrl+f4 doesn't help.
did anyone give a solution to your ticket yet, FarTooNice?
Old thread is old, but I just bought RoA2 and stumbled into the exact same issue, so it's still a thing.
At first I thought the issue was because I play RoA in Dosbox under linux and maybe there is a bug in my configuration, however it turns out to be a general problem. TL;DR solution:
In order to fix the issue, open the files "gamea.inst" and "gameb.inst" with a text editor and replace all occurrences of "Music\" with "C:\Music\" (without the ""). Afterwards changing the CD with Ctrl+F4 works as expected. The issue:
There are 2 CD images, "gamea" and "gameb", both are so called mixed mode CDs, i.e. they contain a data track as well as CD audio. The images are CUE/BIN images, actually "gamea.inst" is the cue sheet (usually named "gamea.cue"), while "gamea.gog" is the bin file (usually "gamea.bin"). The audio files are stored under the MUSIC subfolder as .ogg files, as indexed in the CUE sheet ("gamea.inst").
Now the problem happens when mounting the images within DOSBOX. The images are mounted to drive D:, while the installation folder is mounted to drive C:. I think what happens when you try to switch the CD during the game via CTRL+F4 is that it checks the CUE file for the audio files. However the CUE file just says the .ogg files are under the MUSIC subfolder, which is correct, BUT the MUSIC subfolder is not part of the .BIN file of the CD image (which is mounted to drive D:) but is stored under C:. Therefore the imgmount fails because it does not find the tracks under D:\MUSIC. Changing the references in the CUE sheet to C:\MUSIC fixes the issue. Note that while the CD images work in DOSBOX now, they will likely fail when mounted directly by the host system, because the path C:\MUSIC is probably invalid there now.