Was having this exact issue since updating to 5.2, and found a bug report for it for version 4.6. Looks like someone else is also having the same issue as me since updating to 5.2.
How do we flag this as an issue again, as the ticket is currently closed and marked as fixed?
Got a link? This sounds a lot like the issue I have over here - Anybody got ScrollRects to cooperate with dynamic content? - with the only difference being that it’s not a Canvas being moved (but it is being reset to the lower left corned just by toggling Play/Edit mode)