Screensaver settings reverts

I have my screen saver set to display images from a folder in my ~/Pictures directory, and the "Shuffle slide order" box is checked. In Yosemite, I find that occasionally one or both of those settings will revert to the defaults; the "Source" menu will revert to "National Geographic", the "Shuffle slide order" box will be unchecked, or both.

Is there any reason these settings should be changing without my intervention? Is there any way I can monitor the settings (such as in a system log somewhere) to find out more about when this happens and why?