Wordpress meta query returning same results when checkbox value checked

I am creating a custom plugins which has the ability to search users according to their meta values. Everything is perfect except the part when the checkbox query is checked. If i check the checkbox the query returns 3 same results. The search is working fine as I am getting the desired result but 3 times. Here is my code tried so far.

$users = new WP_User_Query( array(
'search'         => "*{$pem}*",
'search_columns' => array(
    'user_email',
),
'meta_query' => array(
    'relation' => 'AND',
    array(
        'key'     => 'first_name',
        'value'   => $fname,
        'compare' => '='
    ),
    array(
        'key'     => 'last_name',
        'value'   => $lname,
        'compare' => '='
    ),
    array(
        'key'     => 'min_salary',
        'value'   => $salary_min,
        'compare' => '='
    ),
    array(
        'key'     => 'empl',
        'value'   => $status,
        'compare' => '='
    ),
    array(
        'key'     => 'min_hrly',
        'value'   => $salary_hourly,
        'compare' => '='
    ),
    array(
        'key'     => 'years_work',
        'value'   => $years_work,
        'compare' => '='
    ),
    array(
        'key'     => 'years_non',
        'value'   => $years_non,
        'compare' => '='
    ),
    array(
        'key'     => 'expert_work',
        'value'   => $expert_work,
        'compare' => '='
    ),
    array(
        'key'     => 'a_city',
        'value'   => $addr['city'],
        'compare' => '='
    ),
    array(
        'key'     => 'a_state',
        'value'   => $addr['stt'],
        'compare' => '='
    ),
    array(
        'key'     => 'a_zip',
        'value'   => $addr['zip'],
        'compare' => '='
    ),array(
        'key'     => 'startday',
        'value'   => $startdate['day'],
        'compare' => '='
    ),
    array(
        'key'     => 'startmonth',
        'value'   => $startdate['month'],
        'compare' => '='
    ),
    array(
        'key'     => 'startyear',
        'value'   => $startdate['year'],
        'compare' => '='
    ),
    array(
        'key'     => 'hdeg',
        'value'   => $education,
        'compare' => '='
    ),
    array(
        'key'     => 'sekj',
        'value'   => $position1,
        'compare' => '='
    ),
    array(
        'key'     => 'seekk',
        'value'   => $position2,
        'compare' => '='
    ),
    array(
        'key'     => 'checkbox',
        'value'   => $expert['a'],
        'compare' => 'LIKE'
    ),
)
) );
$users_found = $users->get_results();

This problem only arise when I add query for checkbox else everything is working good.

Am I missing something?

via Chebli Mohamed