If ZusiDisplay crashes on start while trying to reproduce, it might be due to this crash that depends on a race condition: https://github.com/ValveSoftware/wine/issues/132 I'm using a patched uiautomationcore.dll for Proton 6.3 with the upstream patch applied, which reliably fixes it for me. Sometimes it works using unpatched Proton 6.3, so who knows what it really depends on. Maybe disk access speed / file caches.
Edit: The patch is part of Proton 7.0 so it should just work.
proton 6.3x1 2022-02proton 7.0x1 2022-02proton 5.13-6x1 2022-02proton 6.3-8x1 2022-02uiautomationcore.dllx1 2022-02
Game: ZUSI 3 - Aerosoft Edition (1040730)
Affected Proton version: 6.3-8
Not affected: 5.13-6
The font added in https://github.com/ValveSoftware/Proton/commit/ca928d31f9964b3e9439fe0e9c5efbad6c57b4c1 as a "Microsoft Sans Serif" alternative appears to have a slightly larger line height compared to the original font.
This causes the "ZusiDisplay" application which is bundled with the game "ZUSI 3 - Aerosoft Edition" (1040730) to have an unusable settings menu. Since all the form elements in the settings are a bit larger because of the font height, the "Speichern" (save) button at the bottom of the window is outside of the visible region of the window. The window is not resizable, so there is no way to save the settings.
This is not an issue with Proton 5.13-6 (which doesn't ship a micross.ttf replacement, but somehow the application now handles this gracefully since the latest application update yesterday, so the menu works - maybe falling back to Arial), but it is an issue with Proton 6.3-8. So it's a regression.
Screenshot using Proton 5.13-6:

Screenshot using Proton 6.3-8:

Steps to reproduce: