I'm sorry you're hitting this issue.
Could you please submit an issue from within Hype, using Help > Report an Issue? When you do so, please also include your document in the Issue Reporter's Attachments section, and ensure that the "Send logs, preferences, and system information" checkbox is checked.
Here's some tips on restoring work if something unexpected happens:
Browse Previous Versions
Select File > Revert To > Browse All Versions
_This opens up Time Machine and lets you go back in time for your document. _
Restore Document From Export
If you exported a version you want to revert to, select Help > Restore Document from Export > Select your
document name.hyperesources folder. This lets you create a new Hype document based on that export.
Press ⌘ + z to undo.