Cannot install/activate conferences module

When trying to install, update, or enable conferences module this morning:

Doctrine \ DBAL \ Exception \ UniqueConstraintViolationException

An exception occurred while executing 'ALTER TABLE meetme CHANGE users users SMALLINT DEFAULT 0, ADD PRIMARY KEY (exten)': SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '2111' for key 'PRIMARY'

/var/www/html/admin/libraries/Composer/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php

case '1701':
return new Exception\ForeignKeyConstraintViolationException($message, $exception);

case '1062':
case '1557':
case '1569':
case '1586':
return new Exception\UniqueConstraintViolationException($message, $exception);

case '1054':

Server/Request Data
HTACCESS on
HTTP_HOST 10.87.60.109
HTTP_USER_AGENT Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:46.0) Gecko/20100101 Firefox/46.0
HTTP_ACCEPT text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8
HTTP_ACCEPT_LANGUAGE en-US,en;q=0.5
HTTP_ACCEPT_ENCODING gzip, deflate
HTTP_REFERER http://10.87.60.109/admin/config.php?display=modules
HTTP_COOKIE lang=en_US; searchHide=1; PHPSESSID=06n131ahfbk19o6osemehdhv50; _ga=GA1.1.227703022.1465817064
CONTENT_LENGTH 0
HTTP_CUDA_CLIIP 10.87.14.201
HTTP_X_FORWARDED_FOR 10.87.14.201
HTTP_CACHE_CONTROL max-age=259200
HTTP_CONNECTION keep-alive
PATH /sbin:/usr/sbin:/bin:/usr/bin
SERVER_SIGNATURE <address>Apache/2.2.15 (CentOS) Server at 10.87.60.109 Port 80</address>
SERVER_SOFTWARE Apache/2.2.15 (CentOS)
SERVER_NAME 10.87.60.109
SERVER_ADDR 10.87.60.109
SERVER_PORT 80
REMOTE_ADDR 10.87.14.201
DOCUMENT_ROOT /var/www/html
SERVER_ADMIN root@localhost
SCRIPT_FILENAME /var/www/html/admin/config.php
REMOTE_PORT 51162
GATEWAY_INTERFACE CGI/1.1
SERVER_PROTOCOL HTTP/1.1
REQUEST_METHOD POST
QUERY_STRING display=modules&action=process&quietmode=1&online=1&modules%5Bconferences%5D%5Baction%5D=install&modules%5Bconferences%5D%5Btrack%5D=stable
REQUEST_URI /admin/config.php?display=modules&action=process&quietmode=1&online=1&modules%5Bconferences%5D%5Baction%5D=install&modules%5Bconferences%5D%5Btrack%5D=stable
SCRIPT_NAME /admin/config.php
PHP_SELF /admin/config.php
REQUEST_TIME 1465818772
GET Data
display modules
action process
quietmode 1
online 1
modules Array ( [conferences] => Array ( [action] => install [track] => stable ) )
POST Data
empty
Files
empty
Cookies
lang en_US
searchHide 1
PHPSESSID 06n131ahfbk19o6osemehdhv50
_ga GA1.1.227703022.1465817064
Session
langdirection ltr
module_name modules
module_page modules
AMP_user ampuser Object ( [username] => admin [id] => [password:ampuser:private] => e089c9056d84e3f943a1c89c6e801831791b2e06 [extension_high:ampuser:private] => [extension_low:ampuser:private] => [sections:ampuser:private] => Array ( [0] => * ) [mode:ampuser:private] => database [opmode:ampuser:private] => [_lastactivity] => 1465818772 )
Environment Variables
empty
Registered Handlers
0. Whoops\Handler\PrettyPageHandler

From CLI:
fwconsole ma install conferences

[Doctrine\DBAL\Exception\UniqueConstraintViolationException]
An exception occurred while executing 'ALTER TABLE meetme CHANGE users user
s SMALLINT DEFAULT 0, ADD PRIMARY KEY (exten)':
SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '2111
' for key 'PRIMARY'

[Doctrine\DBAL\Driver\PDOException]
SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '2111
' for key 'PRIMARY'

[PDOException]
SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '2111
' for key 'PRIMARY'

ma [-f|--force] [-d|--debug] [--edge] [--color] [--skipchown] [-e|--autoenable] [--skipdisabled] [--format="..."] [-R|--repo="..."] [args1] ... [argsN]

I can't access entries to delete the apparent duplicate, I don't even know where the supposed duplicate came from. I've tried uninstalling the module but this apparently doesn't delete the conference room entires.