It's so so to replace game files and load a save...
In this IPL case, here are the issues:
- Some save data references buildings by index (i.e. closely related to the order of items placed by IPLs), those are related to the scm commands SET_VISIBILITY_OF_CLOSEST_OBJECT_OF_TYPE and SWAP_NEAREST_BUILDING_MODEL)
- Binary IPLs shall not be fetched in a different order (from the IMG) because save files store information about them by index on save games.
- Other issues related to enexes, unique jumps, garages.... being also referenced by index
Yeah, current public Mod Loader (0.1.15) is not aware of the second issue, but next version is.
So if you've added or changed the order of some object in the IPLs, and that includes rearranging the order IPLs are loaded, the save game won't work very well. And if you've replaced a binary IPL, it might cause the specific img tool to rearrange the order of the binary IPL, which will, again, make the save game a bit broken.
I can tell you that by looking at the screenshot above, the problem is strongly related to the first issue.