That is why this message explained a lot about what was happening. Even when not attacking multiple times, it occurred. This pointed to a problem with the code handling events (such as hitting), which could happen out of order. So it is no longer a combat problem, but a more general one (which could cause other bugs as well). Several people are looking into this and hopefully will find a fix soon. Since this is a problem deep in the code, it takes time to fix this properly though.