Out of interest, are you listening to the audio on WaniKani during reviews? Also, have you tried the KaniWani audio userscript in conjunction with the above? I found that hearing the audio helps along with having KaniWani set to a 2s delay when correct with high detail so I get to see the kanji more often too.
That and I reset back to level 1 twice on WaniKani (with KaniWani synchronised to the same) before things really felt like they were sinking in.
Also, with multiple failures for certain items, maybe review the meaning/reading sections on WaniKani for the problem items again and try to really visualise narrative in your head.
Finally, do you listen to much native material by way of e.g. Netflix or podcasts? I find hearing vocab that I recognise (even if few and far between!) helps with my random recall.