Online maps as overlay do not update tiles
Base map: mapsforge http://www.openandromaps.org/maps/europe/CanaryIslands.zip
Overlay: Google Sattellite online map (or any other online map)
The overlay maps tiles do not seem to be loaded at all. It looks to me as if an online overlay map does not trigger tile loading.
The other way round works: Google Sat as base map, mapsforge as overlay. Although I have yet found a good blend mode to make that feature worthwile.