I saw that you are using a pretty old version of Aseprite too (v1.2.6), I would recommend you to update it to the latest one (v1.2.25). Anyway there might be some issues with your hard disk too, a common problem on Windows which was fixed on v1.2.7, quoting the release notes:
Aseprite v1.2.7 […]
- Possible fixes for Windows 10 problems:
- Saving files when turning off the computer (t/31)