There is a fundamental design flaw in the Digitone: when in a track you repeat the same note sooner than the release of the patch, the same voice is re-used, leading to a click, even if all the other voices are available. If instead you play a different note, a new voice is used and there isn’t a click.
It is very easy to demonstrate this behaviour. In a fresh track select a factory preset with a longish release, such as an ambient patch. Press lips to show the voice utilization screen. Now quickly play C D E F … C and watch how at each keypress a new voice is used. Then quickly play C C C C: the one voice is reused, and you hear clicks.
I wrote to support about this but they didn’t bother answering. It seems to me a firmware update is seriously needed here, at least to provide an option of using a free voice on a repeated note.