I'm on Windows 10 64-bit, Intel Core i7-2600.
When I open projects I created in Studio One 3 in Studio One 4, the outputs for the VST Kontakt are all messed up. Usually where they were listed as a custom config (st. 1, st. 2, st. 3, etc.) the load is blanked as the default st.1, st. 2, and then surround outputs (these are how the VST first loads initially).
Following this, when you attempt to do ANYTHING with the Kontakt VST in the loaded instrument list in the mixer window, the application crashes.
This does NOT happen with Studio One 4 Projects by themselves, this happens when I have created an older project in v3 and then open it in v4.