Clicking and dragging a citation in VE causes it to vanish (removes it) and clicking Undo or ctrl+Z does not reverse this. It also does not cause the Publish changes button to become active despite the changes having an effect. I proved that it wasn't a visual bug by making other changes first and then clicking and dragging a citation–the Review your changes showed a diff that removed the citation. Cut and paste using ctrl+X and ctrl+V does not cause a problem.

This happened at 2019 Kashmir earthquake.

Could not reproduce this on https://test.wikipedia.org/.

Browser: Version 77.0.3865.90 (Official Build) (64-bit)
OS: macOS