I had similar issues... anki would drill me hard while stuff was still in short term memory (single session) then push it back weeks or months before I had any retention. I'd get to it again and it'd be completely gone, queue re-learning it from scratch.
I brought it up around the time I tried it and got shouted down. Pretty much every spaced repetition app was treating anki like a holy emissary, so I gave up on spaced repetition entirely.