Sorry for the lack of replies. Here are few details what we are doing now.

2 years ago we start working on new graphic engine that was going to be used in future Artstudio Pro. First we were developing Artstudio and the engine simultaneously.
But as the engine was more and more advanced, few months we decided to finally finish it. That's why we temporary almost dropped Artstudio development.

To finish everything in the engine, fix bugs, make optimizations etc we decided to make small note-taking app (vector). We didn't want to use the engine in Artstudio because it could me make Artsudio unstable and buggy.

The note-taking app is almost ready now, and we really love how it works! The strokes are perfectly antialiased and smooth, framerate never drops below 120hz, saving is instantenous.

We also fully switched to SwiftUI and implemented great new UI, with nice draggable panels.

After we finish the note app we will return to Artstudio. It should take 1-2 months for that.

That's the story

Yea, we are not sure if we should use a separate option for Barrel Roll in Brush Editor > Dynamics > Angle...

Yes, i agree. We will try to do it asap.

We are alive!

Could you check if it happens on iCloud / local disk (On My iPad) / both?

it was gone for a bit, but i suddenly started getting the "Document was not saved! Please close and reopen the document" popup every autosave or if i manually save

I have fixed a bug when switching from one textfiled to another. But i'm not sure if this case is also fixed.
Could you give all steps to repeat this issue?

As i wrote few times the bug is caused by iOS.
I reported that to apple, but it seems they haven't fix it yet.
I can easily repeat the bug in apps like Pages or Numbers.

However, like icezimy wrote, i think i finally found a workaround! We are testing that in real work...

Ok, thanks for info.

I found the issue!

I had an old artstudio pro beta app that expired. Once i deleted the beta app, all of the thumbnails began to appear once again