Remember to always sort your objects in the object list. The easiest way to do this is to press the sort button (top of the list, rightmost, with two-arrow-icon). When playing the game the objects are drawn in the same order that they appear in that list, so you have to assure that the objects are sorted correctly (the backmost object in your scene will be drawn first, then the next one and so on). Otherwise you'll get weird results.
If that's what you experienced, then this is not a bug (just for answering your question).