I have both VS 2019 and VS 2019 Preview Installed. I uninstalled VAssistX and reinstalled it. I use version 10.9.2333.0 based on my subscription. When I load VS 2019 everything is fine. Sometimes, when I load VS 2019 Preview its ok, but many times, it shows I have VAssistX Version 10.9.2341.2 loaded, although I didn't install and I didn't run an upgrade. I felt there the software should be able to keep the VS 2019 versions separated since they are in different directories.
I've tried uninstalling and re-installing but the new version always comes back.
I've noticed in 16.3, when I load the program twice, the second one shows the VAssist version as 10.9.2341.2 for some reason.
It sounds like you might be a victim of the Visual Studio auto-updating of extensions. This page describes the situation and how to prevent it from occurring: https://docs.wholetomato.com/default.asp?W426
You will need to disable auto-update in both environments since the settings are independent of each other.