I created a small project that partially mirrors the routing of a real project of mine, but it still demonstrates a bug in the send assignments for the mixer channels.
To reproduce the bug, present since version 2.2.83, follow these steps:
indeed, when I tried creating a new project with version 2.2.83 (but I also tried with 2.2.85 with the same result), the issue, as you stated, doesn’t occur.
I think I understand that the issue occurs when (as happened with my test project) the routing, and specifically the sending in the mixer, was created with a previous VST Live 2 version, in my case, version 2.2.80.
Perhaps (but this is purely hypothetical) the issue I describe in this post is somehow related to what was reported in the post: