Gitlab throws an 500 error when requesting one specific avatar

Out gitlab installation throws sometimes an internal server error when requesting only one specific avatar:

Started GET "/uploads/-/system/user/avatar/4/avatar.png?width=24" for 192.168.63.116 at 2019-02-13 13:10:18 +0100
Processing by UploadsController#show as HTML
  Parameters: {"width"=>"24", "model"=>"user", "mounted_as"=>"avatar", "id"=>"4", "filename"=>"avatar.png"}
Completed 500 Internal Server Error in 10ms (ActiveRecord: 1.6ms)

ActiveRecord::StatementInvalid (PG::InternalError: ERROR:  could not find equality operator for opfamily 1994
: SELECT  "uploads".* FROM "uploads" WHERE "uploads"."uploader" = 'AvatarUploader' AND "uploads"."path" IN ('uploads/-/system/user/avatar/4/avatar.png', 'user/avatar/4/avatar.png')  ORDER BY "uploads"."id" ASC LIMIT 1000):
  app/models/concerns/avatarable.rb:89:in `block in retrieve_upload_from_batch'
  app/models/concerns/avatarable.rb:33:in `retrieve_upload'
  app/uploaders/object_storage.rb:49:in `retrieve_from_store!'
  app/controllers/concerns/uploads_actions.rb:87:in `public_send'
  app/controllers/concerns/uploads_actions.rb:87:in `block in uploader'
  lib/gitlab/utils/strong_memoize.rb:26:in `strong_memoize'
  app/controllers/concerns/uploads_actions.rb:85:in `uploader'
  app/controllers/concerns/uploads_actions.rb:36:in `show'
  lib/gitlab/i18n.rb:55:in `with_locale'
  lib/gitlab/i18n.rb:61:in `with_user_locale'
  app/controllers/application_controller.rb:419:in `set_locale'
  lib/gitlab/middleware/multipart.rb:101:in `call'
  lib/gitlab/request_profiler/middleware.rb:14:in `call'
  lib/gitlab/middleware/go.rb:17:in `call'
  lib/gitlab/etag_caching/middleware.rb:11:in `call'
  lib/gitlab/middleware/rails_queue_duration.rb:22:in `call'
  lib/gitlab/metrics/rack_middleware.rb:15:in `block in call'
  lib/gitlab/metrics/transaction.rb:53:in `run'
  lib/gitlab/metrics/rack_middleware.rb:15:in `call'
  lib/gitlab/middleware/read_only/controller.rb:38:in `call'
  lib/gitlab/middleware/read_only.rb:16:in `call'
  lib/gitlab/middleware/basic_health_check.rb:25:in `call'
  lib/gitlab/request_context.rb:20:in `call'
  lib/gitlab/metrics/requests_rack_middleware.rb:27:in `call'
  lib/gitlab/middleware/release_env.rb:10:in `call'

This only happens periodically, once refreshed the requested ressource is returned correctly. Is this related to gitlab or to psql ?

gitlab-rake gitlab:env:info:

System information
System:		Debian 9.6
Current User:	git
Using RVM:	no
Ruby Version:	2.4.5p335
Gem Version:	2.7.6
Bundler Version:1.16.6
Rake Version:	12.3.1
Redis Version:	3.2.12
Git Version:	2.18.1
Sidekiq Version:5.2.1
Go Version:	unknown

GitLab information
Version:	11.5.4
Revision:	315df49
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	postgresql
Using LDAP:	no
Using Omniauth:	yes
Omniauth Providers:

GitLab Shell
Version:	8.4.1
Repository storage paths:
- default: 	/var/opt/gitlab/git-data/repositories
Hooks:		/opt/gitlab/embedded/service/gitlab-shell/hooks
Git:		/opt/gitlab/embedded/bin/git

gitlab-psql --version:

psql (PostgreSQL) 9.6.8