Definitely get where you’re coming from here, and my personal pet peeve is when I just straight out typo the pronunciation of a word I 100% know and set it back a level. That can get really depressing and if it happens a couple times in the same session I usually stop and come back and do the reviews at a later time.
That said, a few things that have helped me specifically with memory errors for rendaku or unusual pronunciations (or the endless “is this 人 a にん or じん?”) is to:
- use the “extra study” feature or just review manually myself the ones I’m having trouble with (and every month or so checking out wkstats to narrow down which items those are
- install the [Userscript] WaniKani Rendaku Information and [Userscript] ConfusionGuesser to get feedback right away during reviews about which I might be confusing and why a word does or doesn’t rendaku
Maybe that could help you as well?