Interval timer initializes incorrectly

I have Wallch 4.183 running in Linux Mint Mate 17.2. When I boot the computer, the wallpaper clock initializes with a timer interval of approximately 59.8 seconds. This causes the wallpaper clock to not match the system clock. It will never correct itself. However, clicking the tray icon and selecting 'Show' will reset the wallpaper clock and adjust the timer to exactly 60 seconds. This happens on every wallpaper clock I have tried.

It just occurred to me that this may not be limited to the clocks. I set Wallch to change wallpapers every 10 seconds. After re-booting the computer, the wallpaper would change just a little bit quicker than that. Selecting 'Show' reset the interval to exactly 10 seconds.

This is also the case after a logout/login.

Edit: This does only happen when "Start Wallch on System's startup" is selected in Preferences > General.