The drop-down that did nothing
Every list in my Control Plane has an Area filter. Pick Travel and the list narrows to travel. On 2 August I picked an area on the Decisions page and nothing happened. The same day, on the Milestones, Tasks, Ideas and Incidents lists: the same.
The reason was in the code. The filter reads a field on each row, a domain or an area, and compares it with the one you picked. Decisions kept their domain under one name and the work items under another. A row with no field the filter recognised fell through to the last line of the function, return true. The filter hid nothing. It passed all of them.
Why failing open is the bad way
An empty screen gets noticed at once. A screen that shows everything looks like a control that stopped working, and I blamed the click.
It also hides a second problem. On Decisions, 99 of 253 records have no domain at all. Passing those in every area is correct: a record with no domain is unclassified, not unrelated, and hiding it would make the filter destroy what it cannot judge. So "passes everything" is sometimes right and sometimes a bug, and from the outside the two look the same.
It came back on Saturday
On 17 October Claude built the Instructions page, 274 notes, with the same Area drop-down. I picked Travel and nothing changed. The new rows had no field the filter knew, and the same last line passed them all. It was the same bug, eleven weeks later.
Now each row carries the domain of its note, or the area its folder names. Travel leaves 54 of the 274 and Systems 195. A note with no domain of its own, like a handover in a day folder, still passes every area, on purpose, and the page's help text says so.
Claude's check on the NAS was a row count for each choice: Travel 54, Systems 195, All areas 274.