I'm using an arcade stick, the same one I use to play Tekken (it works perfectly in Tekken). I also use my arcade stick to play DMC5 and it works fine there too. Wish I could be of more help honestly but it was really hard to replicate and seemed random, although I have a feeling it has to due with the game stuttering briefly when enemies load in, and the "key/button up" input gets eaten, so it thinks the player is still holding in that direction. This tends to happen in lots of games that kinda just load stuff willy nilly in the middle of gameplay. Let me know if I can help you out!