"Could not retrieve the pipeline status" appeared for some previous merged MR's

gitlab-rake gitlab:check SANITIZE=true

run well, everything is yes, ok, Finished

System information
System:		
Current User:	git
Using RVM:	no
Ruby Version:	2.6.5p114
Gem Version:	2.7.10
Bundler Version:1.17.3
Rake Version:	12.3.3
Redis Version:	5.0.7
Git Version:	2.24.1
Sidekiq Version:5.2.7
Go Version:	unknown

GitLab information
Version:	12.9.2
Revision:	ac5568eb5d8
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	PostgreSQL
DB Version:	11.7
URL:		https://gitlab-01.mgmt.oboz.app
HTTP Clone URL:	https://gitlab-01.mgmt.oboz.app/some-group/some-project.git
SSH Clone URL:	ssh://git@gitlab-01.mgmt.oboz.app:65022/some-group/some-project.git
Using LDAP:	no
Using Omniauth:	yes
Omniauth Providers: 

GitLab Shell
Version:	12.0.0
Repository storage paths:
- default: 	/var/opt/gitlab/git-data/repositories
GitLab Shell path:		/opt/gitlab/embedded/service/gitlab-shell
Git:		/opt/gitlab/embedded/bin/git