The development team has spent the last month completely re-working the logic that governs how dash tiles re-flow.
In the early versions, user attempts to modify complex dashboards occasionally produced unpredictable behaviour in tiles.
Now, even with dashboards with over 100 tiles, they behave very predictably when re-organising or resizing, and viewing on mobile platforms.
You should now have a MUCH better time getting things to look (and stay!) the way you intended.