Data Export XLS Damaged

Hi there,

I encountered a problem when exporting survey data to XLS/XLS legacy/XLS Analyzer. The file is created and downloadable, but it seems to be damaged. When opening MS Excel (and LibreOffice Calc) it says something like “there are problems with parts of the content in [FILENAME]. Shall we try to restore as much as possible? (y/n)”. Choosing “yes” the next prompt says “File is damaged and cannot be opened.” A sample XLS is attached.
FPG_Alltagsmobilität - latest version - False - 2020-03-13-09-58-24.xlsx (11.3 KB)

This applies to all forms of different complexity, independent of containing repeat groups and independet of export settings (include group names, versions, XML/labels).

CSV/CSV Legacy Exports work.

Current version (own server):

kobotoolbox/nginx                          latest 
kobotoolbox/kobocat                        2.019.52-final-shared-database
kobotoolbox/enketo-express-extra-widgets   1.77.0-jnm-grunt-workaround  
kobotoolbox/kpi                            2.019.52-final-shared-database
mongo                                      3.4    
mdillon/postgis                            9.5   
redis                                      3.2

Any ideas on this?

Thanks in advance,
Daniel