InDesign 18.1 x64 will open the de.idml file from the archive attached below* but crashes when trying to open cs.idml. The only difference between these two files is a single AppliedLanguage attribute set in Styles.xml.

Please look into why this happens with only one of them (or if both files are considered incorrect, let us know why).

*What I have attached is a .zip archive renamed to .txt. Please rename it back and extract the two files I've mentioned. Your form did not allow me to upload neither .idml nor .zip files.

Thanks for any help! Arnold