Adobe Reader DC 2018.009.20044 very slow when opening password protected PDF on Terminal Server (windows 2008r2)

The Terminal Server hat 50 connected Users.

When opening a not password protected file, it goes fast. When the document is password protected, 30 seconds.

What it tried until now:

- Remove all plugin files from C:\Program Files (x86)\Adobe\Acrobat Reader DC\Reader\plug_ins

- deactivate protected mode

- tried to work with ProtectedModeWhitelistConfig.txt file + registry HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Adobe\Acrobat Reader\DC\FeatureLockDown bUseWhitelistConfigFile=0 key

"

FILES_ALLOW_ANY = c:\*

EVENTS_ALLOW_ANY = MS*

REG_ALLOW_ANY = HKEY_CLASSES_ROOT\*

REG_ALLOW_ANY = HKEY_CURRENT_USER\*

REG_ALLOW_ANY = HKEY_LOCAL_MACHINE\*

REG_ALLOW_ANY = HKEY_USERS\*

REG_ALLOW_ANY = HKEY_CURRENT_CONFIG\*

"

when activating logging, seems to work:

[02:21/11:24:47] Adobe Reader Protected Mode Logging Initiated

[02:21/11:24:47] Found custom policy file: C:\Program Files (x86)\Adobe\Acrobat Reader DC\Reader\ProtectedModeWhitelistConfig.txt

[02:21/11:24:47] Adding custom policy: FILES_ALLOW_ANY = c:\*

[02:21/11:24:47] Adding custom policy: EVENTS_ALLOW_ANY = MS*

[02:21/11:24:47] Adding custom policy: REG_ALLOW_ANY = HKEY_CLASSES_ROOT\*

[02:21/11:24:47] Adding custom policy: REG_ALLOW_ANY = HKEY_CURRENT_USER\*

[02:21/11:24:47] Adding custom policy: REG_ALLOW_ANY = HKEY_LOCAL_MACHINE\*

[02:21/11:24:47] Adding custom policy: REG_ALLOW_ANY = HKEY_USERS\*

[02:21/11:24:47] Adding custom policy: REG_ALLOW_ANY = HKEY_CURRENT_CONFIG\*

[02:21/11:24:48] Unexpected CreateKey for: \REGISTRY\MACHINE\Software\Adobe

[02:21/11:24:48] Real path: \REGISTRY\MACHINE\SOFTWARE\Wow6432Node\Adobe

[02:21/11:25:00] Invalid path: \Device\HarddiskVolume1\Users\admin_sainte\AppData\Local\Adobe\Acrobat\DC\

[02:21/11:25:00] Invalid path: \Device\HarddiskVolume1\Users\admin_sainte\AppData\Local\Adobe\Acrobat\DC\

[02:21/11:25:00] Invalid path: \Device\HarddiskVolume1\Users\admin_sainte\AppData\Local\Adobe\Acrobat\DC\

[02:21/11:25:20] Exit Code:1

but still slow.

I don't have a clue what i still can try?

Anyone had the same problem?

Any kind of help appreciated.