I feel really bad, it seems like such a low level to hit a block on. But man I am strugglebusing. Getting into the vocab for energy, letter, life, substitute, and a few mixed others has me hitting some serious doubt.
First thing first. Do. Not. Give. Up.
While you may think level 4 is some low level thing and not an achievement, you’ve made it this far. Further than you’ve been before. You can do it because you CAN do it.
With the mandatory pep talk out of the way (and I am being serious; do NOT give up), my recommendation is, take it slow if you have to take it slow.
Take notes as you do the reviews you are failing at consistently. Write the kanji down. Write the vocab down. You don’t know stroke order (maybe you do?) but the act of just trying to write it absolutely helps solidify it in your mind. Write the mnemonics down as well. As counter productive as it may seem, just physically putting it on paper will help your mind keep it in place; you are telling your brain this IS important.
Will this help you get 100% every single time it pops? Probably not. I still struggle with the vocab for put down; I see it, but I struggle with the recall of the reading because, well I just do. Every time I miss it, I write it all down again and I am pretty close to just having it down finally.
And read the mnemonic every time you see it; think about it, feel it, taste it. Whatever that mnemonic says, just focus on really getting it. Most of them are easy to recall but sometimes when I have an issue really getting a word or Kanji down, I have to go this far to keep it in line.