Can't rearrange Dashboard panels in 2019 Week 13

Observed Behavior:
It looks like in 2019 Week 13, changes aren’t saved when dragging and dropping panels in the “Arrange Panels” dashboard view.

I added a new panel to a dashboard and it appeared below the “Create Panel” / “Add Existing Panel” button pair. I then attempted to drag it up in the column and no purple placeholder appeared.

I then dragged the existing panels below my new panel, and while they looked okay in the Arrange preview, the changes weren’t saved. I verified by looking at the phabricator_dashboard.dashboard table that the layoutConfig JSON wasn’t changing.

I changed the JSON in the database directly to fix it for the time being.

I know you’re redoing all the dashboard editing on master right now, so if you want me to just ignore this until next week lands with the new dashboard editor, I won’t be too irked.

Expected Behavior:
When I drag a panel, it should move.

Phabricator Version:
Internal fork from 2019 Week 13; same as the other ticket I just filed.

Reproduction Steps:
Upgrade to 2019 Week 13 Stable
Edit a dashboard (I tested with the two-column layout)
Add a new Panel to the bottom of the first column
Attempt to drag the new panel to the top of the first column
Find yourself inexplicably stymied
Investigate the code for a little while
Run an UPDATE on mysql

I suspect this is pre-existing to at least some degree. It’s getting a pass soon under https://secure.phabricator.com/T13272 and will probably be resolved in Week 14.