That's weird, that error might mean that I have to rework on a lot of things, never occured to me, can you download the game again? I added a code that will probably fix that, I also made a lot of performances improvements. Please let me know if this bug or any happens again.
You did put your agumon and gabumon to sleep and closed the game, right? and now it isn't letting you acess their data. I think the bug persists still, I'm reworking their stats and stamina system, soon I'll be posting a devlog with the update, this bug will be fixed by that.