I am in exactly the same boat. Been using Cubase since the VST days so when I saw this app I jumped at it.
When the app works it’s ideal, a genuine quality MAW. Unfortunately it has a tendency, as the OP says, of wiping out large chunks of work when hitting undo.
To be frank, this is simply not good enough. I would perhaps be more understanding if this behaviour was exhibited by an app from a new/small developer with limited budget and/or resource and/or experience but come on, you guys are Steinberg and this is Cubase. The very LEAST I would expect of an app from an established developer at this price mark is stability. The very least.
This really does need fixing very soon. I know the update cycle is roughly a monthly one and we should be expecting an update end of May but, for me, this issue should be treated as a huge priority; a fix should be dropped before the regular update. Failing that, as the OP said, some very clear information about what is being done to resolve the issue and when it will be fixed is a must.
To the OP
Did you know that audio can be recovered by fishing it out of the trash? I only ask as this was a recent discovery for me and has helped a little.
I have not found a similar workaround for MIDI and the overall arrangement is still lost (don’t get me started on snapshots) but you may be able to recover some of your work