Closed Unassigned: Category item list count is zero [176]

For any project (and we have about a hundred) the list under the "Category (open issues)" header in the Project Summary page shows 0 as the issue count for any category. And only the unassigned category displays relevant count. The projects have plenty of issues in any kind of state.

v.1.5.258.0. Survived several upgrades since 0.9.

Please advise.