I’d like to give some input in this topic too. I have the same (or very similar) problem.
tldr: I could not load BIG ableton projects on touchable with server version 420, I still cannot with 424. Small project load fine.
I work with a huge ableton project, which I use for my live performances. I have been using touchabe for over three years now. With touchable V3 any kind of such problems did not occur, I only used to sometimes have difficulty connecting, but once connected all worked well. Maybe a week ago, I’ve ran into connectivity problems again and found that there is this new version touchable Pro and tried to install it. So small projects load fine. They load perfectly with touchable V3 on iPad and with touchable Pro on the same iPad (both using the new touchable pro server v420). When I load the big project I was talking about, touchable V3 (iPad) just crashes and shuts down and touchable Pro kind of loads, but I cannot see any of my tracks, volume sliders and so on. Just like the OP, I can press PLAY and STOP, but nothing more.
Getting ready to post here on the forum, a couple of days passed and I’ve found this thread. Got excited, as I found that the latest version for the server now is v424. However, I’ve tested the new version (done reboots, script reinstalls, updated iPad app) but all seems the same regarding my problem.
I have not tried to delete all tracks in the big project, like the OP did, but all newer and lightweight projects load ok.
One more detail, which may help figure out the problem is: When touchable fails to load a big project, I cannot see the “red square” in my macbook ableton window. (The one that outlines which tracks are visible in touchable on the iPad. Maybe because nothing is visible on the iPad.)