Layering tracks--skipping and distortion... Why??

When I add tracks after adding more than two tracks the playback skips and distorts. Any idea why?

I bought an ipad mini-- 16G-- is that why? Does it need to be 32G or 64G to work properly?

Thank you.

Hello,

could you be a little more specific about what kinds of tracks you are adding?

Kind regards,
Frieder