Update showed version button breaks JSON fields

[gorgeousvlad]

Bug report

Describe the bug

Clicking Update showed version button causes incorrect data serialization for JSON fields

Before clicking:

After:

Steps to reproduce the behavior

1. Go to Content Manager -> <Your collection with JSON field>
2. Click on collection instance
3. Add data to JSON field
4. Save it
5. Press Update showed version button
6. Update page
7. See error

Expected behavior

Update showed version button clicking doesn't change JSON fields data appearance