Version 2 is currently in beta testing and a few beta testers have pointed out that the reels disappear sometimes.  This is true if you allow another window to appear over the top of Picture Slots.  The reason for it is complex, but a quick explination is as follows.

In version 1.x of Picture Slots each Reel was an Image Object in its own right, but I concluded that this was resource hungry and because I hate programs that consume resources needlessly I figured there must be a better way to do it, so I removed 15 image objects from the window and decided to paint the reels directly to the window canvas.  This reduced the memory footprint of Picture Slots by 2.1 Megabytes which I was very happy about, but the down side it seems is that when a window appears over the top of Picture Slots the Reels vanish.  It would appear that by painting directly in this way means that the Reels aren't actually there and when the Window is repainted the Reels aren't being put back.

If anyone knows how to fix this problem I would be interested to hear from you.

The bottom line is that I am aware of this and hope to have it resolved before version 2 is released.

UPDATED INFORMATION

I think this is fixed in version 2.2 and above.