Updated to Alpha 2.703.
Pressing any modifier keys shows default control strip. Releasing the modifier leaves me in default Touch Bar until I switch window.
Device information:
I had the same issue. Went back to 2.702
Ah I think I can reproduce it. You can downgrade to the previous version via https://folivora.ai/releases
Should now be fixed in v2.704 alpha 
Have a new issue with it. In groups, the option "Show always (Don't care about modifiers at all)" fails to work. Items still hide once I use a modifier key. Find the problem in this attached JSON file. (Had to export it into it's own preset as the JSON explores the character limit).
BTT Bug Report.bttpreset (1.1 MB)
Ah, this is not a new issue though, or is it?
I think it should now work in v2.705 alpha
Indeed! It works! Thank you!
Your preset seems to work correctly here with that version. What is not working for you?
My system crashed earlier this day. I provide further information once it works again.
Sorry, some BTT Script deleted my desktop, and till I got it and then found how to create a new one (with is super easy actually…) I lost some time.
So, here we go.
Ah I see. The problem was that buttons that have the "Close currently open Touch Bar group" are always shown (so the default close button is always visible), ignoring the modifier settings. I have adapted the logic slightly, it should now work in 2.707 alpha
