Render in place error

When i work on my compositions, i render my kontakt instruments, omnisphere instruments and so on from midi to audio files.
In most cases, i use render in place as separarate files.

Sometimes, cubase 10 combines 2 midi tracks to a single audio track, but most of the rendered files of a render session are correct.
Visually i can easily find the wrong rendered files and render them again afterwards again.

In Cubase 9.5 there have not been those render issues.

Does they belong to my midi settings ?
Btw. .I always use rack-VSTis.

Or is it a known issue of Cubase 10 ?