Is there a maximum limit to the number of aircraft profiles you can have stored on the iPad?

I have 12 at the moment covering various types and registrations, but every now and then, one of them will disappear from my device, forcing me to "Open from Cloud", which is really annoying. An even worse scenario is when one profile wasn't backed up to cloud storage and then disappears. I haven't been able to identify a trend yet or timescales - it seems random.

So, whats causing aircraft profiles to disappear?

Cheers