Why are likes on my photos disappearing and reappearing?

[ruby11]

I get the notification for each person liking my photo when i first went on to the photo there were 10 likes which was the same as the notification.Then later when I checked the photo again it said 10 likes still but when i clicked to see who liked it there were only 6 names, then later it changed to only 6 likes on the photo- so i thought people may have unliked it, but then when I check again later all 10 likes (and all 10 names) are there again. Why is it doing this? I deactivated my account a couple of times in the last month, could that be causing it?