Ok I'll test yet if that's issue of Orux format, specific zoom or generally of any personal maps
Edit: I reproduce this bug on these conditions:
Personal map in OruxMaps format zoom 18, magnify 100%
Click wpt, choose edit, change position by selecting new coordinates from map, change, save
Now the view is set to maximum available zoom layer and magnified to 6400% and map not rendered.
Map rendering is restored only after reopening map or magnifyimg out to senseful level and
changing to previous zoom level.