I assume it just has to do with save-game from before Natural Gas was changed to Propane and Vegemite was added. So this likely won't affect newer save-games.
Simply change the manufacturing process and the issue should be resolved.
It is common that removed or changed manufacturing processes cause weirdness to existing save-games. Might be a good idea to implement a failover state when an already running manufacturing process is removed or drastically changed. Maybe have it becomes disabled and inoperable, but retain some information about what it was producing so a player can see what was changed and figure what production changes they might need to change.
Simply change the manufacturing process and the issue should be resolved.
It is common that removed or changed manufacturing processes cause weirdness to existing save-games. Might be a good idea to implement a failover state when an already running manufacturing process is removed or drastically changed. Maybe have it becomes disabled and inoperable, but retain some information about what it was producing so a player can see what was changed and figure what production changes they might need to change.