bit of a silly tip, but i find that sometimes ignoring what method your own mind tells you to do and plugging in the 4 or 5 answer options to see if they fit correctly works as a last resort option for me when i'm stuck and/or running out of time. and when you're at home, sometimes saying out loud what steps you're using to solve the problem makes it clearer for you and you can avoid silly mistakes. like "okay, so the lcm of these is gonna be... yup. now i check against each option..." and just narrating it to yourself. that way you sometimes notice repetition in the method for a question and can recognise easier when it's going to be similar to another question you've done before. that stuff helps in the long run, i think, because then problem solving might start to feel more familiar and less scary, perhaps? i don't know if these'll work for you but it can't hurt to try them out next time you do a mock. i hate problem solving too tbh.
but these are just some things that work for me when i do prep. i'm sitting mine this year too so i don't know if i'm in much of a position to give advice haha. let me know if you ever want to chat about the tsa though, or go through a question. it'd be good practice for both of us. what course are you applying for if you don't mind me asking? wishing you the best of luck on your test x