I have a Williams System 9 Space Shuttle doing the same thing. However I swapped a good working aftermarket DE/Williams supply in and it still does the same thing. However my issue is slightly different. The game boots and will even play and upon booting the scrolling display issue isn’t happening yet. If you either leave it in attract mode or play it after about one minute it starts with the scrolling displays and what’s different about this issue is when it starts doing that it shuts down power to the flippers and game except for lights as well. Turn off and back on and it works again for 30 seconds to 1 minute. Weird issue I haven’t come across before. Any suggestions?

Well turns out my issue was with the display board on Space Shuttle. I booted the game without the ribbon cables connected to the board and no more power loss to flippers and game. Bought new board on eBay and installed and it’s as good as me now. I am going to try and fix the board but for now it’s good to go.