"mentioned in" appears in wrong group/project

groupR/projectR uses Redmine as external issue tracker.

groupG/projectG uses GitLab issues.

When a commit with message like "Fixes #910 (closed)" (nb: referring to Redmine issue ID) pushed to groupR/projectR ,

"mentioned in" appears in the issue #17 (closed) in groupG/projectG.

A strange thing I noticed was when I accessed http://gitlab.foo.bar.com/groupG/projectG/issues/910 ,

I was redirected to http://gitlab.foo.bar.com/groupG/projectG/issues/17 .

Other IDs like 909 or 911 did not cause this, neither did .../groupR/projectR/issues/910 .

(nb: group names and project names here are fake but issue IDs (#910 (closed) and #17 (closed)) are actual although I am not sure if those ID values matter.)

I have no further clue at the moment.

Any suggestion where to look at further would be highly appreciated.

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GitLab 8.8.5

GitLab Shell 2.7.2

GitLab API v3

Git 2.9.0

Ruby 2.1.8p440

Rails 4.2.6

Mysql2 5.5.49-0ubuntu0.14.04.1