I don't know if this will help anyone or if it has been already stated, but you could try inputing the command for the next action of your combo at the start-up animation for your first action and repeat. I am finding that the game still reads the commands properly and your character performs the next action.
Also, someonne mentioned half circles and (double) quarter circles on D-Pad. Take it slow and patiently input the command(s). Let's say you were in the middle of a mix-up and then wanted to finish with a DD. Basically, take your time and input the command for the DD during the last mix-up animaton you're in before you plan on using the DD. Make sure you properly make the motion, it should come out. There's plenty of time to do it.