When I press multiple buttons at the same time, they come out one after each other instead of (basically) at the same time on my QMK firmware keyboard (melody 96).
e.g. I press "wasd" at the same time, i'll get w -> was -> wasd instead of just "wasd" immediately in games (tekken in this case)
There's a few names for this, like "chord splitting" but I can't really find a fix for it.
I had an ikbc one and a razer one which both don't have this issue and from what I've seen every QMK based keyboard has this issue so it's a firmware problem, not a hardware one.