Could be a zoom/resolution issue, as your background image seems stretched and your borders, for themselves, not distorted. I imagine you've already checked, but just to be sure:
- check your map size (maybe it changed?)
- check your device zoom (maybe you are entering the editor with a lot of outward zoom, so the map background (behind the actual map image) stretches to fit your zoom)
- map image doesn't match map size (results in distortion)
You said it keeps moving your borders, which is quite weird. Though little, chance is, the issue lies in one of these.