I found something that feels like a bug with the sliders, but I've only seen it happen on a single map so far (didn't test very many maps). It's like the slider gets "caught" on the end with like an extra beat and so you have to hold it at the end of the slider while the ball seems to spin in place for that beat.
Map in question (Normal):
https://osu.ppy.sh/s/2585
It's fairly close to the beginning (the slider is shaped like an upside down question mark) and should be noticeable by having one of the slider beat stars on the actual end.
Map in question (Normal):
https://osu.ppy.sh/s/2585
It's fairly close to the beginning (the slider is shaped like an upside down question mark) and should be noticeable by having one of the slider beat stars on the actual end.