Found a defect using MF with firmware version 3.0.0.1959.
The “Sample”-oscillator has been selected. (Also other oscillators using samples are affected). Using “Shift” + “Type” will show the sample selection screen. Entering this screen quickly after existing, and turning the “Type” key, sometimes results in the selection screen being all black with a white bar (see picture).
The oscillator itself will stop creating sounds, like no sample has been selected.
After a while, the sample can be selected again, and the oscillator will function again.