It’s a fair guess that a multitrack recording going beyond 60 mins is using up all of your iPhone’s RAM, and that’s why Cubasis is crashing.
Cubasis has to store all your recorded track data until you close the Project, and depending on how many tracks, that could be a LOT of data.
A newer M-Series iPad will give you double the RAM of an iPhone 11, but it to, will eventually run out of RAM.
Maybe what you need is to record to a computer, not a mobile device.
OR, break up your recording into manageable parts, if possible.
Such as 45 minute sections.
That’s what I’d try.
I’d save my empty multitrack project setup as a template, which I’d duplicate and renumber for each section. You can do all that within Cubasis.
In the template, I’d remove any plugins I wasn’t using;
For example, the following plugins are loaded by default in a New Project.
Insert Effects: Channel Strip, StudioEQ
Send Effects: Reverb
Mixer, Master fader: Master Inserts, Brickwall
I’d replace all those and any other plugins I’m not using.
from each and every Insert Effects, Send Effects, and Master Inserts with None (no instrument or effect).
Otherwise, a computer might be your best solution.
John