Hi Landon,
Thank you for the question and I am sorry about the issue!
Have you tried the latest BIMx app? Even with the old BIMx apps, I rarely have issues with open big files on my iPad Pro. With the latest BIMx app on iOS, we will be able to open much bigger files on iOS devices.
Looking forward to hearing from you!
Best regards,
Minh
Minh Nguyen
Technical Support Engineer
GRAPHISOFT