Sorry about your rejections - these are always quite difficult.
I think firstly, it is important to note that rejections are inevitable in this process even for 1st class graduates and applicants with strong work experience. As such, it is important to understand that the rejection does not always reflect on your grades or written application responses. Secondly, it would be good to maybe revisit your answers and see whether they are extremely tailored to the firm, have you had interactions with the firm, work experiences that link to the firm, and if your work experience sections are detailed and highlights transferable skills.
As you have gotten to Acs before and you are progressing through test stages with other firms, I wouldn't be too worried in these instances. Different firms focus on different parts of the application and its not always quite easy to understand what these factors are.
In light of this, keep your chin up and keep applying! Best of luck.