No fix. Its a 'bug/feature'.
Never resize/minimize or move the editor while a map is open.
And save your work often.
Dont get frustrated with the editor, youll get used to the rather capricious handling .
Edit: name your terrain with maximum of 8 letters.
The make map feature on Editor2 doesnt work, you have to download editor1 to make maps. the how youll find in a recent thread i started: clipboard maps.