I’m sorry for the late reply. It’s so annoying that nobody answers any questions in the GarageBand community >:(
It may just be the software or the iPad itself. It’s probably too old to handle an app like GarageBand that can easily take up gigs of storage. (I have a few techno and orchestrated songs and a bunch of ringtones, and my GarageBand takes up almost 4.5 gigs.)
Did you ever notice a pattern of the time that it crashes? (For example: when uploading a project to iCloud, downloading a sound pack, or simply opening the app.) The time that it crashes might help us to figure out why it crashes in the first place.