Have to change Password every time I login for admin user

Hi,
Every time I have to change my admin user password, by using “Lost your password” link, which emails me the link to change the password.
Any idea why is this happening?

Please tell me whether the following issue is creating the problem:

My WP site started giving error: “An error occurred while processing this directive” and then every plugin started behaving erratically. Now, when I go to Dashboard and “Deactivate” it, it gives the same error as above.

My error log showed this:

[09-Oct-2015 10:50:54 UTC] PHP Notice: Undefined property: WLMAuthorizeNetARB::$forms in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/lib/integration.shoppingcart.authorizenet-arb.init.php on line 246
[12-Oct-2015 03:45:33 UTC] WordPress database error Illegal mix of collations (latin1_swedish_ci,IMPLICIT) and (utf8mb4_general_ci,COERCIBLE) for operation ‘=’ for query SELECT wp_redirection_items.*,wp_redirection_groups.position AS group_pos FROM wp_redirection_items INNER JOIN wp_redirection_groups ON wp_redirection_groups.id=wp_redirection_items.group_id AND wp_redirection_groups.status=’enabled’ AND wp_redirection_groups.module_id=1 WHERE (wp_redirection_items.regex=1 OR wp_redirection_items.url=’/20…è?’) made by require(‘wp-blog-header.php’), require_once(‘wp-load.php’), require_once(‘wp-config.php’), require_once(‘wp-settings.php’), do_action(‘init’), call_user_func_array, WordPress_Module->init, Red_Item::get_for_url, W3_Db->query, W3_DbCache->query, W3_DbCallUnderlying->query, W3_Db->query, W3_DbProcessor->query, W3_Db->default_query
[18-Oct-2015 07:26:37 UTC] PHP Warning: file_get_contents(): php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854
[18-Oct-2015 07:26:37 UTC] PHP Warning: file_get_contents(https://wishlist-marketplace.s3.amazonaws.com/trigger.txt): failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854
[18-Oct-2015 07:27:08 UTC] PHP Warning: file_get_contents(): php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854
[18-Oct-2015 07:27:08 UTC] PHP Warning: file_get_contents(https://wishlist-marketplace.s3.amazonaws.com/trigger.txt): failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854
[18-Oct-2015 07:27:11 UTC] PHP Warning: file_get_contents(): php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854
[18-Oct-2015 07:27:11 UTC] PHP Warning: file_get_contents(https://wishlist-marketplace.s3.amazonaws.com/trigger.txt): failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854
[19-Oct-2015 09:19:34 UTC] PHP Warning: file_get_contents(): php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854
[19-Oct-2015 09:19:34 UTC] PHP Warning: file_get_contents(https://wishlist-marketplace.s3.amazonaws.com/trigger.txt): failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854
[19-Oct-2015 09:19:34 UTC] PHP Warning: file_get_contents(): php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854
[19-Oct-2015 09:19:34 UTC] PHP Warning: file_get_contents(https://wishlist-marketplace.s3.amazonaws.com/trigger.txt): failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854
[19-Oct-2015 09:19:35 UTC] PHP Warning: file_get_contents(): php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854
[19-Oct-2015 09:19:35 UTC] PHP Warning: file_get_contents(https://wishlist-marketplace.s3.amazonaws.com/trigger.txt): failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854
[19-Oct-2015 09:19:35 UTC] PHP Warning: file_get_contents(): php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854
[19-Oct-2015 09:19:35 UTC] PHP Warning: file_get_contents(https://wishlist-marketplace.s3.amazonaws.com/trigger.txt): failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/finandr1/public_html/blog/wp-content/plugins/wishlist-member/core/Class.php on line 854

Now, the Wishlist Member plugin got deleted automatically and my member-only program is visible on my site.

What should I do?