Symptom

On a Board-layout view grouped by swimlanes = "Parent issue", some sub-issues with a valid parent link never render in their parent's swimlane. Browser Ctrl-F confirms the card isn't in the DOM at all on that view. The issue renders correctly on every other view I've tried (issue detail page, Table layout, list views).

Repro

• Project has one Epic-style issue with 51 sub-issues (linked via addSubIssue / real sub-issue relationship, confirmed via GraphQL issue.parent and issue.subIssues).
• Board view: layout = Board, filter = cycle:"<current cycle>", swimlanes = "Parent issue", columns grouped by Status.
• The swimlane header for the Epic shows a progress count of 32/51. 17 sub-issues have Status=Planned and should appear under the Epic swimlane; some do, some don't.
• Example: sub-issue #2285 has parent.number == <epic> via GraphQL, has Cycle = current cycle, Status = Planned, Issue Type = Bug, is on the project (not archived, single project item). It doesn't appear on the Board view. It appears fine on the Table view and on its own issue page.

What I've verified via the API

For the missing sub-issue:

• issue.parent returns the correct parent.
• issue.projectItems returns exactly one item on the project, not archived.
• All relevant fields are set: Status, Cycle, Issue Type, Team, Assignees.
• fieldValueByName("Parent issue") returns null — but it also returns null for sub-issues that do render correctly in the swimlane, so that null is not diagnostic.

Workarounds tried, none fixed the board rendering

1. Re-setting Status to its existing value (to force Projects v2 to re-resolve cached fields) — no effect.
2. removeSubIssue then addSubIssue — no effect.
3. deleteProjectV2Item then addProjectV2ItemById with all custom fields restored — no effect. Fresh project item id, same view behavior.

Workarounds that DO work

• Changing swimlanes from "Parent issue" to "No swimlanes" — all items render.
• Switching layout from Board to Table (keeping groupBy = "Parent issue") — all items render.

So the bug is in the Board-layout + swimlane=Parent-issue rendering path specifically, not in the underlying data or the Table layout.

Possibly related

• Sub-issues not visible when grouped by Parent Issue #167057 — same "sub-issues invisible when grouped by Parent issue" symptom, reported on Table view with a smaller epic (30 sub-issues). Still unresolved. Ours may be the Board-layout variant of that bug, possibly correlated with sub-issue count.

Ask

• Confirmation of the bug and ETA for a fix.
• Whether there's a current sub-issues-per-epic rendering limit on the Board layout.
• Any server-side action needed to re-index the project view.