Ive been having issues with readings not matching mnemonics on certain kanjis. For example 葉 has a mnemonic for the reading は, but only accepts よう as the answer.
I also have the same issue with 横. It will not accept よこ as the reading, even though the mnemonic is for よこ.
I tried searching the forum for similar issues, but couldnt find anytjing.
This was caused by an issue with the API that got fixed a few weeks ago. You need to reset the database to get the corrected version.
For more details see:
If in doubt, head to the thread of the app when you have issues like this, as you’ll find it posted at length in there (and you might also find the thread I posted about it in the API and Third Party Apps section letting people know about the issue) 
Also, while I’m here…
\textcolor{pink}{\huge \textsf{WELCOME! ^-^}}
Even if you’ve been a member for a while, so aren’t really new hehe
Take the time to check out the FAQ and GUIDE if you haven’t already…
…but you probably have, because you seem like you’re diligent and awesome like that ^-^
There’s also a lot of good stuff on the forum to help you…
…that you’ve likewise probably already seen, but it still worth mentiioning!
The Ultimate Guide for WK
The Ultimate Additional Japanese Resource List
The New and Improved List of API and Third-Party Apps
I hope that you continue to enjoy WaniKani that your worship of the Crabigator is eternal!
