I've found that our project is not rendering properly on windows direct3d9 target (Direct3d11 build fails with runtime error for unknown reason, and I did not try Direct3d12 due to SDK not installed). It works ok on other targets, including windows opengl.
It also begin to works good if I disable nine-slice images, and these are currenly the only images that have "non-standard" indices in my index buffers. This and the way the picture is damaged makes me think that the problem is with index buffers.
I tried many different things including recording actual vertex and index buffers and dispalying them in test project, but bug did not reproduce.
In the beginning of september it was working. And there were no changes in our render code since that.
I understand that that is not enough information, but may be somebody knows what can I try to do to solve this issue?
This is how it looks (and the image is not stable, it differes frame to frame):