I guess it’s related to the thread were no audio is played at all. See my post there:
Basically, I tested a few scenarios, and the interesting thing I found was that if I use my University VPN then the audio plays noticeably later. I usually have a relatively fast internet connection, therefore the audio plays immediately and I never noticed it. But when I turn on the VPN, there will be an additional delay, and I hear the sound often only 1-1.5 seconds later.
I would suggest that if autoplay is enabled, then the audio should be prefetched - but right now it doesn’t.
WaniKani is currently changing a lot on their backend to improve it long-term, but short-term it definitely feels a bit “work-in-progress”. Maybe we can send them an e-mail (or hope a mod notices this thread) so that this issue gets on their current issue tracker, so they can improve it in the next updates 