yo do old verison saves not work on the update I was playing 4 I think and updated to 6 had most of the game done
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Slot 30 is used for the autosave so it's not a problem. Did you copy the entire save folder from the previous version into the new one? People often try to transfer only the save files they use like 1 or 2 but the game uses global data files to track a number of variables.
If you did so and the problem still persists - send me your zipped save folder from the previous version and I'll check it out.