Also keep a wrong answer journal. You'll start to see patterns of why you usually miss stuff. For me its not targeting what the conclusion says fully

I have gone from 145 diagnostic to 162. What helped me the most was before doing timed drills, for each untimed question I would write out:

1. The main point/conclusion

2. Why/a general summary of the evidence

When I did this I found my foundational reasoning greatly improved. I often found common mistakes are not specifically targeting the conclusion enough, targeting something in the argument that ISN'T THERE, and not truly fully understanding what it's saying. Once you keep doing this you'll find for all question types the common trend is directly targeting the exact wording of the argument and understanding the exact wording of the evidence. You'll start the see with the questions you miss "oh! I wasn't paying close enough attention to what the conclusion EXACTLY says". Or "Oh I only targeted half the conclusion but didn't fully encompass its details enough"

Once you bring this foundational skill up, you can do timed drills and then your mistakes will be more minor mistakes such as mixing up conditional reasoning, misreading, misunderstanding a single word, etc. Your score indicates you are missing a foundational skill. Please do this for several untimed drills FIRST and then dive into timed once you can fully understand these two points without having to write them out.