"Access denied" error disappears after executing command for the 2nd time

[ghost]

I'm using drush to reinstall a module so that .install is executed.
I run:
drush pmu medialib
drush en medialib
...and I get an error on after the latter command:

The following extensions will be enabled: medialib
Do you really want to continue? (y/n): y
WD node: Exception: Access denied. in medialib_node_presave() (line 381 of [error]
/srv/www/htdocs/project/sites/all/modules/medialib/medialib.module).
exception 'Exception' with message 'Access denied.' in [error]
/srv/www/htdocs/project/sites/all/modules/medialib/medialib.module:381
Stack trace:

0 [internal function]: medialib_node_presave(Object(stdClass))

1 /srv/www/htdocs/project/includes/module.inc(951): call_user_func_array('medialib_no...', Array)

2 /srv/www/htdocs/project/modules/node/node.module(1106): module_invoke_all('node_presave', Object(stdClass))

3 /srv/www/htdocs/project/sites/all/modules/medialib/medialib.api_common.inc(538):

node_save(Object(stdClass))

4 /srv/www/htdocs/project/sites/all/modules/medialib/medialib.install(390):

_medialib_create_directory_raw('Media Library', NULL)

5 [internal function]: medialib_enable()

6 /srv/www/htdocs/project/includes/module.inc(922): call_user_func_array('medialib_en...', Array)

7 /srv/www/htdocs/project/includes/module.inc(497): module_invoke('medialib', 'enable')

8 phar:///usr/local/bin/drush/commands/core/drupal/environment_7.inc(143): module_enable(Array)

9 phar:///usr/local/bin/drush/commands/pm/pm.drush.inc(1167): drush_module_enable(Array)

10 [internal function]: drush_pm_enable('medialib')

11 phar:///usr/local/bin/drush/includes/command.inc(366): call_user_func_array('drush_pm_enable', Array)

12 phar:///usr/local/bin/drush/includes/command.inc(217): _drush_invoke_hooks(Array, Array)

13 [internal function]: drush_command('medialib')

14 phar:///usr/local/bin/drush/includes/command.inc(185): call_user_func_array('drush_command', Array)

15 phar:///usr/local/bin/drush/lib/Drush/Boot/BaseBoot.php(67): drush_dispatch(Array)

16 phar:///usr/local/bin/drush/includes/preflight.inc(66): Drush\Boot\BaseBoot->bootstrap_and_dispatch()

17 phar:///usr/local/bin/drush/includes/startup.inc(325): drush_main()

18 phar:///usr/local/bin/drush/drush(114): drush_startup(Array)

19 /usr/local/bin/drush(10): require('phar:///usr/loc...')

20 {main}

...but when I execute the same command again I get:

array_values() expects parameter 1 to be array, null given library.inc.php:123 [warning]
The Betterawstats engine generated the error below. If it is a configuration error concerning AWStats locations [error](i.e. the AWstats data directory, library directory, or language direction), these must be set using the
Statystyki BAW administration pages.
The Betterawstats engine generated the error below. If it is a configuration error concerning AWStats locations [error](i.e. the AWstats data directory, library directory, or language direction), these must be set using the
Statystyki BAW administration pages.
The Betterawstats engine generated the error below. If it is a configuration error concerning AWStats locations [error](i.e. the AWstats data directory, library directory, or language direction), these must be set using the
Statystyki BAW administration pages.
The Betterawstats engine generated the error below. If it is a configuration error concerning AWStats locations [error](i.e. the AWstats data directory, library directory, or language direction), these must be set using the
Statystyki BAW administration pages.
The Betterawstats engine generated the error below. If it is a configuration error concerning AWStats locations [error](i.e. the AWstats data directory, library directory, or language direction), these must be set using the
Statystyki BAW administration pages.
The Betterawstats engine generated the error below. If it is a configuration error concerning AWStats locations [error](i.e. the AWstats data directory, library directory, or language direction), these must be set using the
Statystyki BAW administration pages.
The Betterawstats engine generated the error below. If it is a configuration error concerning AWStats locations [error](i.e. the AWstats data directory, library directory, or language direction), these must be set using the
Statystyki BAW administration pages.
The Betterawstats engine generated the error below. If it is a configuration error concerning AWStats locations [error](i.e. the AWstats data directory, library directory, or language direction), these must be set using the
Statystyki BAW administration pages.
The Betterawstats engine generated the error below. If it is a configuration error concerning AWStats locations [error](i.e. the AWstats data directory, library directory, or language direction), these must be set using the
Statystyki BAW administration pages.
The Betterawstats engine generated the error below. If it is a configuration error concerning AWStats locations [error](i.e. the AWstats data directory, library directory, or language direction), these must be set using the
Statystyki BAW administration pages.
The language file could not be found in this location: /usr/share/awstats/lang/awstats-en.txtPlease check your [warning]
config.php. The value of $BAW_CONF['path_lang'] has to point to the directory where awstats stores its language
files (typically somewhere /cgi-bin/awstats/lang). Please also make sure that php has read-permissions on that
folder.
The library files could not be found in this location: /usr/share/awstats/lib/operating_systems.pmPlease check [warning]
your config.php. The value of $BAW_CONF['path_lib'] has to point to the directory where awstats stores its library
files (typically somewhere /cgi-bin/awstats/lib). Please also make sure that php has read-permissions on that
folder.
The library files could not be found in this location: /usr/share/awstats/lib/domains.pmPlease check your [warning]
config.php. The value of $BAW_CONF['path_lib'] has to point to the directory where awstats stores its library
files (typically somewhere /cgi-bin/awstats/lib). Please also make sure that php has read-permissions on that
folder.
The library files could not be found in this location: /usr/share/awstats/lib/robots.pmPlease check your [warning]
config.php. The value of $BAW_CONF['path_lib'] has to point to the directory where awstats stores its library
files (typically somewhere /cgi-bin/awstats/lib). Please also make sure that php has read-permissions on that
folder.
The library files could not be found in this location: /usr/share/awstats/lib/worms.pmPlease check your [warning]
config.php. The value of $BAW_CONF['path_lib'] has to point to the directory where awstats stores its library
files (typically somewhere /cgi-bin/awstats/lib). Please also make sure that php has read-permissions on that
folder.
The library files could not be found in this location: /usr/share/awstats/lib/mime.pmPlease check your config.php.[warning]
The value of $BAW_CONF['path_lib'] has to point to the directory where awstats stores its library files (typically
somewhere /cgi-bin/awstats/lib). Please also make sure that php has read-permissions on that folder.
The library files could not be found in this location: /usr/share/awstats/lib/mime.pmPlease check your config.php.[warning]
The value of $BAW_CONF['path_lib'] has to point to the directory where awstats stores its library files (typically
somewhere /cgi-bin/awstats/lib). Please also make sure that php has read-permissions on that folder.
The library files could not be found in this location: /usr/share/awstats/lib/browsers.pmPlease check your [warning]
config.php. The value of $BAW_CONF['path_lib'] has to point to the directory where awstats stores its library
files (typically somewhere /cgi-bin/awstats/lib). Please also make sure that php has read-permissions on that
folder.
The library files could not be found in this location: /usr/share/awstats/lib/search_engines.pmPlease check your [warning]
config.php. The value of $BAW_CONF['path_lib'] has to point to the directory where awstats stores its library
files (typically somewhere /cgi-bin/awstats/lib). Please also make sure that php has read-permissions on that
folder.
The library files could not be found in this location: /usr/share/awstats/lib/status_http.pmPlease check your [warning]
config.php. The value of $BAW_CONF['path_lib'] has to point to the directory where awstats stores its library
files (typically somewhere /cgi-bin/awstats/lib). Please also make sure that php has read-permissions on that
folder.

These AWSTATS errors doesn't matter. I get them all the time because I don't have AWSTATS installed. I didn't remove them just in case.

To sum up: executing drush command for multiple times changes the outcome which is not a good practise.