Evo champion William Peter Hjelte, better known as “Leffen”, has spent his time in Super Smash Bros. Ultimate dissecting many of its new properties. During his stress test he’s found that Nintendo’s new platform fighter has some odd quirks when it comes to its new buffer system, most notably in the way it implements the c-stick during aerials.
Many of the problems with the C-Stick are likely attributed to the fact it is a macro, which you can read about in further detail here in this reddit thread.
Sources: reddit; William Hjelte