Save games from old versions.

[Wolf119]

You have to find  an opportunity to make save games form old alpha versions work on new ones ! Like prison architec!!

[SpaceDorf]

I bet prison architect had savegame breaking updates, as every early release game had.
Minecraft had them, Dwarf Fortress had them.
Rimworld had updates that conserved saves and sometimes it screws saves because it is technically not possible to change so much of the game without changing the inards of the game so much, that it can't  use the old stuff anymore. .