Row always returns to its original location. Tried with Safari 12.0.2 and Chrome 71.0.3578.80.
I tried with my own code (used to work), and with the a couple of examples (including one on your site):
1) http://jsfiddle.net/h4wrmfx3/764/
2) https://editor.datatables.net/examples/extensions/rowReorder.html
This would seem to be a common issue, but didn't see any other recent questions in the Forum about the issue.