I'll take a look shortly.

Normally, when an issue is moved to the "done" (or "won't fix", etc) state, a "post function" on the transition should set the resolution appropriately.

That's certainly the case in the "Agile simplified workflow for DM with reopen" which is being used by these tickets.

However, that workflow was only just applied, moving away from the default "jira" workflow. It's possible the "jira" workflow wasn't setting resolution appropriately, or that it somehow got garbled in the change of workflows.

I've re-applied the "done" status to all the affected issues (there were five of them: INFRA-71, INFRA-75, INFRA-76. INFRA-78 & INFRA-79), and the resolutions have now all been set appropriately.

I don't think this should recur, unless there's some need to change the workflow again in the future.

Thank you for helps!
Looking at workflow management page [1], newly created projects has its own copy of default workflow, which is quite different from our standard (for now) "Agile simplified workflow for DM with reopen". I've switched FIBERALOC and SURVEY to the default.
I suppose these tickets from non-DRP projects had such default workflow, and this kind of strange behavior happened.

*1 https://pfspipe.ipmu.jp/jira/secure/admin/ViewWorkflowSchemes.jspa

Added comment to INFRA-90 to add into procedure manual.