Digitone to Cubasis (iPad) sync issue

Hi all,

I’ve come up against an issue:
I’m recording my Digitone into Cubasis via the AUM app (or Ape Matrix). I have the Digitone slaved to Cubasis which works fine - I press play on Cubasis, and the Digitone plays to tempo.

Now I want to lay in another pattern in sync with Cubasis at a particular part of the track, and specifically I want to loop that part to sculpt the pattern in real time before recording.

The problem happens when I play somewhere much later in the song, the clock completely fails and the Digitone plays out of sync with Cubasis.

Any ideas?