Ubooquity 2.1.0 forgets Password?

I run Ubooquity on a raspberry pi. Everything works fine when I start and configure it as admin. But when I restart the raspberry and want to login (after starting with

java -jar /opt/ubooquity/Ubooquity.jar --libraryport 2202 --adminport 2001 --remoteadmin --headless

I cant login. the webadmin.cred file is not empty and when I delete it I can´t give me a new password, only when I delete all files except the jar-file. the permissions on the ubooquity folder is

drwxr-xr-x 6 pi   pi   4096 Aug  1 20:24 ubooquity

and for the files

drwxr-xr-x 4 pi pi     4096 Aug  1 20:14 cache
drwxr-xr-x 2 pi pi     4096 Aug  1 20:14 fonts
drwxr-xr-x 2 pi pi     4096 Aug  1 20:14 logs
-rw-r--r-- 1 pi pi     1141 Aug  1 20:17 preferences.json
drwxr-xr-x 2 pi pi     4096 Aug  1 20:14 themes
-rw-r--r-- 1 pi pi  5431296 Aug  1 20:24 ubooquity-5.mv.db
-rw-r--r-- 1 pi pi     8861 Aug  1 20:24 ubooquity-5.trace.db
-rwxr-xr-x 1 pi pi 19226792 Jul 22 13:35 Ubooquity.jar
-rw-r--r-- 1 pi pi       64 Aug  1 20:16 webadmin.cred

The console writes:

20170801 20:33:56 [qtp31847001-34] INFO  com.ubooquity.d.a - Password provided for admin is wrong. Access denied. [ip:192.168.0.17]

What is wrong, why can I not login from my Notebook (Windows 10, Firefox) as long as I do not restart my rasp or stop Ubooquity I have acces on my books, I can configure everything and it works fine.

Any Ideas?

Thanks Dieter