The problem was strangely only appearing on Mac (in all browsers, Chrome and Firefox included) which was weird given the nature of the code. But anyway, I've patched up the script a bit and tested it a couple of times - the running horse appears on add horses when clicked on continue to payment or save for later, and nothing from the flow of the form is amiss (as far as I've tested, which I hope holds true for all cases).

Please give it a test run at your convenience and let me know if it works for you now. Sorry for getting back to you so late on this, I've been trying to resolve the issue for a while now.