Problem with gifs in Faststone image viewer

For gifs with small dimensions, Faststone seems to work fine. However, if the gif dimensions are larger than the screen size, the following problems occur:
- the gif will open, zoommed into the center
- changing the fit options settings does nothing (this is true even for smaller gif, however)
- if I try to zoom in or out, the directions are inverted (ie. if I press - it will zoom in and if I press + it will zoom out; if I navigate to a smaller gif, the uninverted effect will carry over)
- I cannot navigate/scroll within the large gif, ie. the arrow keys and mouse do nothing, the only way to view the rest of the gif is to zoom out
- once I zoom out of the large gif, there are many artifacts in the gif. The artifacts show up consistently as small black dots around the movement in the gif. Note that I have opened the same same gifs in Windows Photo Viewer and Firefox, which do not show these artifacts.