the #1 problem we see in custom remixes is Bad/Sloppy Transitions between minigames
some minigames you have to press the button repeatedly in a rhythm until a cue happens, some minigames you only press the button when a cue happens, some minigames you have to press and hold (or unhold) the button. it's possible to bridge the gap between these kinds of minigames, but many times we'll come across a custom remix on youtube that does not understand how to properly execute this, and it completely takes us out of the groove.
for example, a problem we come across a lot is going straight from needing to tap to needing to wait for a cue. this causes a situation where if you were to actually play this minigame, it would be impossible to just follow the rhythm and cues and get a perfect, which all custom remixes should aim to be doing
of course, this is easier said than done, as making a custom remix is a lot harder than it seems. lots of moving parts, having to find what minigames match the music, ect. it's no surprise there's mistakes! it's just something on our mind whenever we go to watch one of these