I have this problem as well, first updated the theme and plugin and afterwards I had updated to WP 4.8.
Overwriting the swift framework plugin (which was already version 2.5.43) seemed to have fixed the problem, but an hour later its back again. Yes I have cleared my cache on both my browsers (chrome and Safari) but nothing seems to help.
Is there a fix ?
Help! I need to work on 2 sites based on your themes this week and this is a mayer problem!!!