Tried to clear website data but it doesn’t work. I looked for the error log, and now it’s from KanjiDamage mnemonics for WaniKani. Disabling this userscript and now it’s working fine for the review. 
For lessons I tried to disable Katakana Madness and it works fine now. I installed Katakana Madness few days ago, I’m pretty sure there’s something there.
So actually this issue has been raised while ago [Userscript] WaniKani Katakana Madness - #52 by mickos