multilayer-map with different borders is messed up

i created a single mobac multilayer map like this:

zoom 1-5: google maps, area is complete planet
zoom 6-8: opencyclemap, area is europe
zoom 9-12: microsoft map, area is germany
zoom 13-15: hikebikemap.de, area is munich
zoom 16-18: google satellite image, area is a small part of munich

when doing this in mobac, it requires moving around maps in the list via d&d so it ends up in a single orux sqlite database.

dont know if this kind of map is supposed to work at all, but handling in orux is a bit strange. like it only displays a single tile of the outer maps, the rest of the screen stays empty.

I have a similar problem, it appears to happen as you zoom out, the surrounding tiles don't load as you would expect.
I experience this with a full map of Rome at level 14 then Rome split into 1/4's listed a NW, NE, SW, SE at levels 16, 17, 18.
Again using Sqlite.