Key notes:
The save file is an upgraded one from the beta version
(Not sure if relevant, but I experienced this error after I tried to load the save file while dead)
Restarting did not fix it
Judging by the error file, it might be something related to endosymbiosis. (I have used endosymbiosis prior in this save, the process started in the beta version, I upgraded the save and finished it in the proper release)
Yep, I can confirm that this is an issue when trying to load a save with a placed endosymbiosis action done in the editor. Luckily the fix is really simple by this time remembering to mark the constructor the JSON loading system should use for the endosymbiosis action. I had written that constructor before but I forgot to put the right JSON marking attribute on it so it didn’t work.
I’ve made a fix:
With that fix your save file will load correctly. The fix will be in the next release.