Did you already rebuild the engine prime Database on the internal ssd? perhaps deleting it and creating a new can improve. If all this fails, pls ask @JWiLL for additional denon support.
yes … I even deleted the formation and reformatted it …
however, my problem persists 
I just do not know how to go on …
and @JWiLL don’t answer me …
I know @JWiLL was on vacation but he should be already back, but jet he has not answered me either. Maybe he is very busy.
Where did you buy the players? perhaps the retailer can help. I’ve seen that you are from Germany, so you can call Denon DJ/ inmusic in Ratingen and ask them for help/support:
Für Produktanfragen und technische Beratung kontaktieren Sie bitte unseren Customer Support unter
inMusic GmbH Customer Support Harkortstraße 12-32 D-40880 Ratingen Deutschland Tel: +49 (0)2102 / 7 40 22 0-150 Fax: +49 (0)2102 / 7 40 22 00-11 Email: kundenservice | at | inmusicbrands.com