NoClassDefFoundError on export user list from GW Admin Conso

Hi all,

we have GW Admin Console 18.1.0 installed. Since then it is not possible any longer to export a user list. The java error is:

java.lang.NoClassDefFoundError: org/apache/http/message/BasicHeaderValueParser

The GW Admin Console is:
Build Number:132269
Revision:18.1.0
Build Date:Oct 24, 2018 15:46:43
User Agent:Mozilla/5.0

Does anyone know this error and know how to fix it? We have more than 1000 resources which I have to check on equal name problems and more. That's why I need the list as .csv export and would be happy for any suggestion to solve this problem.

Thanks and regards,

Anne