There is the Wanikani Later Crabigator script that moves items to the end of the queue. that doesn’t put them back into lessons or make them disappear from future review sessions.
OP I think it’s best to accept that you will acquire leeches. A LOT of them making your way to lv 60.
It’s best to just realize that for every level you do, there will be a handful of items that are harder than the rest. But, putting a bit of extra effort continuously using the Extra study “recent mistakes” and the Self-Study Quiz or Item Inspector, and you shouldn’t get overwhelmed by their number.
Reviewing leeches only is often pretty depressing as you start to forget that you actually have capacity for learning, even though these items tend to be slippery and unmemorizable almost. ^^; Mixing it up with “normal” reviews is defo preferable, so you can see your own improvements, even as you also struggle at times. Just my own opinion.