I use DO9 but this also happened in DO8. To use the play/pause/tile/etc buttons in the gif animation viewer I have to double-click each button and even then, it will skip to the next photo and apply whatever button I'd pressed to that, so then I'll have to go back to the previous photo (the one I'd originally wanted).
This happens all the time, it doesn't come and go and persists even after restarting DO/my computer. However, this only happens using the standalone viewer, using the viewer pane works fine (only click once on each button and all perform as expected).
Any suggestions? I don't know if it makes a difference, but I use a laptop/touchpad (the drivers are fully up to date).