while i cant really explain why exactly that happens to you i can definetely assure youre not being the only one in that regard.
In my case, i first discovered this when playing osu, where also over the years, the slower songs became a lot more difficult to execute.

Id guess that its a muscle memory thing by (logically over time) playing a lot more faster, more difficult songs rather than lower bpm ones.

I usually miss notes there because im too early, never because im too late^^.

But im sure that a few reruns will fix this=) and dont get caught up too much about yourself about seemingly "mustFCs", (maybe) rather change up your daily routine to consist of high and low bpm-songs to learn to.

Not sure where i got this from, but "spreading" the learning can be important; e.g playing one fast song and then one slow song will at the end yield faster improvement, afaik.

Anyways, its known, but its not uncommon. And im sure its just a temporary thing:D

Have a good one!=)

I mean I suck at all of them haha :)

Well first of all, twombtorial is one ♥♥♥♥♥ of a track with awful charting on every difficulty.

Secondly, slower doesn't mean easier. In fact many of the hardest tracks are some of the ones with the lowest BPMs but more complex patterns.

Thirdly, rhythm games in general and especially some like this one can have very wonky timing on slower notes (and latency/sync/etc... in general). And it might sound counterintuitive but sometimes faster note chains are more forgiving than slower, isolated notes. I hit a lot more perfects on a hard song than on medium.

And last but not least, it's just a natural phenomenon of how people progress when learning skills, especially rhythm based skills. Individual skills in a skillset might fluctuate, decay and go back up as you progress. It's actually a nightmare for people with imposter's syndrome, because it always feels like you used to be better at whatever you are trying to improve at.

It's pretty normal and typical in music for people to struggle with more precise, slower notes, especially if they have a habit to play fast and sloppy.