I will post this because it may help someone...maybe. I was unable to play Shiny Days on my system at first, i got the freeze after a few minutes of playing, and playing on full screen was an instant freeze. ( I'm on windows 10)
Then i tried this: run Shiny Days, then open your Task Manager. Find SHINYDAYS in the list of processes and right-click "go to details". From this new list, right-click SHINYDAYS.exe and go to "set priority" and change it to Above Normal, and go to "affinity" and uncheck all the CPUs except for one (CPU 0 or CPU 1). This for me fixed the freeze and even the fullscreen bug. I know everyone has their own issues with this game but i figured it can help someone to post this, cya guys, have a nice week-end!