The answer there is that the problem is docker mautic related - so see my problem as follows:
I set up Mautic via docker-mautic behind a nginx reverse proxy instance using a valid ssl subdomain. Mautic isn't aware of that, generating http-forcing submit link in forms -> page is marked as insecure. As solution requires cleaning the cache - I did so - and mautic is not working any more.
### Change Url and Secure Cookie setting ###
172.19.0.5 - - [08/Jun/2017:10:25:32 +0000] "GET /s/dashboard HTTP/1.1" 200 50240 "https://<masurl>/s/config/edit" "Mozilla/5.0 <more UA data>"
172.19.0.5 - - [08/Jun/2017:10:25:58 +0000] "GET /s/forms?_=1496917527832&mauticUserLastActive=1&mauticLastNotificationId= HTTP/1.1" 200 25211 "https://<masurl>/s/dashboard" "Mozilla/5.0 <more UA data>"
### Rebuild forms ###
172.19.0.5 - - [08/Jun/2017:10:26:30 +0000] "POST /s/forms/batchRebuildHtml?ids=[%221%22]&mauticUserLastActive=1&mauticLastNotificationId= HTTP/1.1" 200 25854 "https://<masurl>/s/forms" "Mozilla/5.0 <more UA data>"
### DELETION of app/cache ###
172.19.0.5 - - [08/Jun/2017:10:28:13 +0000] "GET / HTTP/1.1" 301 590 "-" "Mozilla/5.0 <more UA data>"
172.19.0.5 - - [08/Jun/2017:10:28:15 +0000] "GET / HTTP/1.1" 301 590 "-" "Mozilla/5.0 <more UA data>"
172.19.0.5 - - [08/Jun/2017:10:28:15 +0000] "GET / HTTP/1.1" 301 590 "-" "Mozilla/5.0 <more UA data>"
### Repeatingly ###
[2017-06-08 09:30:03] mautic.NOTICE: Doctrine\DBAL\Exception\TableNotFoundException: An exception occurred while executing 'SELECT p0_.id AS id_0, p0_.name AS name_1, p0_.is_published AS is_published_2, p0_.supported_features AS supported_features_3, p0_.api_keys AS api_keys_4, p0_.feature_settings AS feature_settings_5, p0_.plugin_id AS plugin_id_6 FROM plugin_integration_settings p0_ INNER JOIN plugins p1_ ON p0_.plugin_id = p1_.id': SQLSTATE[42S02]: Base table or view not found: 1146 Table 'mautic.plugin_integration_settings' doesn't exist (uncaught exception) at /var/www/html/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php line 53 while running console command `mautic:messages:send` [] []
[2017-06-08 09:30:03] mautic.NOTICE: Doctrine\DBAL\Exception\TableNotFoundException: An exception occurred while executing 'SELECT p0_.id AS id_0, p0_.name AS name_1, p0_.is_published AS is_published_2, p0_.supported_features AS supported_features_3, p0_.api_keys AS api_keys_4, p0_.feature_settings AS feature_settings_5, p0_.plugin_id AS plugin_id_6 FROM plugin_integration_settings p0_ INNER JOIN plugins p1_ ON p0_.plugin_id = p1_.id': SQLSTATE[42S02]: Base table or view not found: 1146 Table 'mautic.plugin_integration_settings' doesn't exist (uncaught exception) at /var/www/html/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php line 53 while running console command `mautic:broadcasts:send` [] []
[2017-06-08 09:30:03] mautic.NOTICE: Doctrine\DBAL\Exception\TableNotFoundException: An exception occurred while executing 'SELECT COUNT(*) AS dctrn_count FROM (SELECT DISTINCT id_10 FROM (SELECT m0_.is_published AS is_published_0, m0_.date_added AS date_added_1, m0_.created_by AS created_by_2, m0_.created_by_user AS created_by_user_3, m0_.date_modified AS date_modified_4, m0_.modified_by AS modified_by_5, m0_.modified_by_user AS modified_by_user_6, m0_.checked_out AS checked_out_7, m0_.checked_out_by AS checked_out_by_8, m0_.checked_out_by_user AS checked_out_by_user_9, m0_.id AS id_10, m0_.title AS title_11, m0_.description AS description_12, m0_.lists AS lists_13, m0_.network_type AS network_type_14, m0_.revision AS revision_15, m0_.stats AS stats_16, m0_.properties AS properties_17, m0_.publish_up AS publish_up_18, m0_.publish_down AS publish_down_19 FROM monitoring m0_ WHERE m0_.is_published = ? AND (m0_.publish_down IS NULL OR m0_.publish_down >= ?) AND (m0_.publish_up IS NULL OR m0_.publish_up <= ?)) dctrn_result) dctrn_table' with params [1, "2017-06-08 09:30:03", "2017-06-08 09:30:03"]: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'mautic.monitoring' doesn't exist (uncaught exception) at /var/www/html/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php line 53 while running console command `mautic:social:monitoring` [] []
[2017-06-08 09:32:02] mautic.NOTICE: Doctrine\DBAL\Exception\TableNotFoundException: An exception occurred while executing 'SELECT p0_.id AS id_0, p0_.name AS name_1, p0_.is_published AS is_published_2, p0_.supported_features AS supported_features_3, p0_.api_keys AS api_keys_4, p0_.feature_settings AS feature_settings_5, p0_.plugin_id AS plugin_id_6 FROM plugin_integration_settings p0_ INNER JOIN plugins p1_ ON p0_.plugin_id = p1_.id': SQLSTATE[42S02]: Base table or view not found: 1146 Table 'mautic.plugin_integration_settings' doesn't exist (uncaught exception) at /var/www/html/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php line 53 while running console command `mautic:campaigns:trigger` [] []
[2017-06-08 09:35:01] mautic.NOTICE: Doctrine\DBAL\Exception\TableNotFoundException: An exception occurred while executing 'SELECT p0_.id AS id_0, p0_.name AS name_1, p0_.is_published AS is_published_2, p0_.supported_features AS supported_features_3, p0_.api_keys AS api_keys_4, p0_.feature_settings AS feature_settings_5, p0_.plugin_id AS plugin_id_6 FROM plugin_integration_settings p0_ INNER JOIN plugins p1_ ON p0_.plugin_id = p1_.id': SQLSTATE[42S02]: Base table or view not found: 1146 Table 'mautic.plugin_integration_settings' doesn't exist (uncaught exception) at /var/www/html/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php line 53 while running console command `mautic:campaigns:rebuild` [] []
[2017-06-08 09:38:01] mautic.NOTICE: Doctrine\DBAL\Exception\TableNotFoundException: An exception occurred while executing 'SELECT l0_.is_published AS is_published_0, l0_.date_added AS date_added_1, l0_.created_by AS created_by_2, l0_.created_by_user AS created_by_user_3, l0_.date_modified AS date_modified_4, l0_.modified_by AS modified_by_5, l0_.modified_by_user AS modified_by_user_6, l0_.checked_out AS checked_out_7, l0_.checked_out_by AS checked_out_by_8, l0_.checked_out_by_user AS checked_out_by_user_9, l0_.id AS id_10, l0_.name AS name_11, l0_.description AS description_12, l0_.alias AS alias_13, l0_.filters AS filters_14, l0_.is_global AS is_global_15 FROM lead_lists l0_ ORDER BY l0_.name ASC': SQLSTATE[42S02]: Base table or view not found: 1146 Table 'mautic.lead_lists' doesn't exist (uncaught exception) at /var/www/html/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php line 53 while running console command `mautic:segments:update` [] []
[2017-06-08 09:39:30] mautic.ERROR: SCHEMA ERROR: An exception occurred while executing 'SELECT f.alias, f.is_unique_identifer as is_unique, f.type, f.object FROM lead_fields f WHERE f.object = 'lead' ORDER BY f.field_order ASC': SQLSTATE[42S02]: Base table or view not found: 1146 Table 'mautic.lead_fields' doesn't exist [] []