Thanks for bringing this to our attention; multiAdd looks to be working fine on both of your sites now. We rolled out a minor update to our cart code about a week ago in preparation for future developments, with a few more tweaks since then, so the issue could have cropped up anytime in the past week. We had confirmed that multiAdd still worked in these rollouts, but something about your particular setups were unusual edge cases our Developers had to examine closely to resolve. We do apologize for the inconvenience.