Given the recent OS X update to High Sierra, it's possible there are some bugs unique to Safari. I know I've experienced a few of these outside of Travian which is often the case once a browser updates.
If you've already tried the fix Dario suggested, message Support in-game for the servers affected and they can feed this on. On initial inspection it appears the OSx update has caused the code to hiccup in a couple of places.
#AskTravian - Episode 4 is now available! Watch it here!