Hey! So I added an awful lot of code between V1.4 and V1.5, most of which is initialised upon starting a save file - as a result, old save files had a risk of being corrupted, since it featured new code that was never properly initialised since that process occurs on starting a new save file.
To compensate for this I added a "Casual" mode, which doubles all drop rates in the game to get you back on your feet a little sooner.
Early access for this game is planned for the first quarter of 2026 - that will be a completely separate system, meaning a new save file then too, so it's up to you if you want to start from scratch again only to have to restart again upon the game's full launch.
Apologies for the issues with your current save file - it's somewhat out of my control this early in development unfortunately, I'm constantly improving and updating internal systems, but that then makes newer versions incompatible with older save files.
This sort of thing will not be an issue by the time Early Access rolls around, since by that point all of the foundations will have been built, so no bugs should be present that cause save files to be lost.
Sorry again for this issue, the game is currently in a rapidly changing state and it's very difficult to ensure consistent functionality across versions,