I'm certain there's a bug in the editor that is related to rendering, however I'm not entirely sure of the cause. When it does happen, there's usually a lot of different objects on the screen, and while they sometimes 'disappear' completely, other times they appear in the wrong place as if they had the wrong vertex transform (sometimes even with 3D rotations!). Like the others, if I disable effect previewing, it stops happening. Whatever the cause, I'm fairly certain that a vertex transform is involved.
Maybe you could make a special editor build that rebuilds the vertex transform matrix from scratch before rendering each object, and we can see if the bug stops? This is obviously impractical as a permanent solution for performance reasons, but for diagnosing the issue, it could be useful.
Edit: if I move all objects with effects to their own layer, the problem stops completely. It seems objects with effects don't like rendering after 9-patches, but keeping them on separate layers makes it a non-issue. But, if this happens, EVERYTHING after them disappears (or moves to someplace odd), even on separate layers.
Edit: Objects with tint effects have this bad interaction with 9-patches, but objects with brightness or swirl effects do not appear to.
Edit: I created this capx to show the minimum requirements for the bug. I think I've also identified the last requirement. If you just open this file, you might not notice anything odd. But, if you were to add a ton of objects, then the problem will start. Alternatively, if you simultaneously open another project that has a lot of objects, this will also trigger it. So, if you can't replicate the issue, try opening as many large projects as you can.
Edit: The plot thickens! I was going to try and use 3D Ripper DX to see if I could get more info. But, it only appears to work with 32-bit applications (and only DirectX, C2 is OpenGL ). So, I installed the 32-bit version of Construct 2, and the problem stopped. This bug has a ridiculous list of requirements. Lets see:
1. Must use Construct 64-bit.
2. Must have effect previews enabled.
3. Must have a 9-patch in your layout.
4. Must have another object in the same layer as the 9-patch, and rendering after it (above in z-order) with a Tint effect.
5. Must have a lot of objects loaded (texture memory usage?)
Yeah, I think I'm done looking at this.