Config import conflict, how to remove lock
My specific issue was that Redis module update to 1.0 brought with it new redis.services.yml file in the module. Updating my site's Redis services file, in sites/default/, resolved the issue. 

What was happening was that the alreadyImporting() method of ConfigImporter defaults to true, when in fact my mis-configuration would have been returning an error I think.

This issue pointed me in the right direction: https://www.drupal.org/project/redis/issues/2996655

If it had been a simple lock issue the following should have worked I think:

drush ev "\Drupal::lock()-&gt;release('config_importer');"