Great news! Fiorella, who was really getting tired of playing the harpsichord and chimes modes of her digital piano, can once again also use all three piano-piano modes without them squawking and creaking at her. Husband had fooled around under the instrument, Fio had called an expert who never showed up, but it was Fio herself, electronic nitwit that she is, who did the job, and it's so embarrassing.
She turned the keyboard off, then turned it back on again. Apparently digital pianos aren't supposed to be kept running for fifteen years without pause. Who knew?