Map sometimes shows empty tile places even though the tile is in cache

As you can see from the attached images, on zoom level 17.42, the SE corner of the view is displayed correctly, but when adjusting the zoom slider a bit, to 17.5, the empty tile appears. Moving the slider further, the map appears again. All three images are using the same tile, so it should be at hand.
Similar thing comes up sometimes when adjusting the mapviewer window size. At certain size a blank tile appears, but if you continue e.g. expanding the window, it shows again. It can be repeated, so that the certain size is always showing blank tile. But if you pan a bit, the blank spot can no longer be seen with the previously non-working size.

This issue is different from the issue that sometimes a tile just isn't loaded. Those tiles don't show up no matter how much you pan or zoom (within zoomlevel).