Steps to reproduce:
- Select text
- See a "picture" of the text moving
- Release the text where it belongs
- The "picture" disappears
- Nothing happened.
Drag and drop seems to work in Firefox.
See also https://en.wikipedia.org/wiki/Wikipedia:VisualEditor/Feedback/Archive_2017_1#Text_disappeared_during_editing.2C_when_I_tried_to_drag_wording_down_the_page which might (or might not) describe a similar problem in Chrome.