I can relate, more than half of my leeches are due to word similarities as well. In particular, they tend to happen if two similar words start appearing at roughly the same time (if a word has had enough time to "consolidate" well in my memory before a similar word appears, I tend to be OK).

When this happens, I find the Anki "leech" feature to be useful. I just let it remove (suspend is the word, I guess?) those words automatically. Flashcards are not my sole learning method, so I will probably learn them anyway by other means at some point, so spending lots of time on repetitions to get them right is not worth it.