In all of my projects I use a side-chain trigger on a track with no direct output that sends to a Cubase compressor on a group channel. I always set that trigger track on Solo Defeat, so when I need to check other tracks in Solo that are routed to that group channel, the side-chain compression keeps working.
After I save, close and reopen the project, the Solo Defeat setting gets forgotten and I need to re-enable it. It is a very small nuisance, but I thought it mention it anyway.
This has been a long-standing issue, and I just created a new topic with some additional context and specificity about this for CUBASE 13! As this post is six years old and never received a reply, it seems like a duplicate topic was warranted.