Some segments not working on 7 segment multi led digital clock
It's very Soviet looking. Those large LED displays were frequently made with series LED dice so if there is an open connection the whole segment will go out. If the display digit or display is potted there's not a heck of a lot you can do other than replace the entire bad part.
Maybe swap the MS digit? You might be able to rotate it 180° to get working segments but the connections won't likely be exactly mirror images.