That was probably the ketchup itself that had leaked from one or more of the packets. It gets real sticky like that. Yeah it's got a lot of sugar. Sometimes in restaurants we would wash the whole batch when that happened but if you don't find the one or more that was leaking, it doesn't really work out too well.
I used to find and report sticky ketchup packets at 5G's condiment bar, at stores that did not have the large ketchup dispenser. All the stores in my area now have the dispensers.