I got also 33 % and even 0 % on last attempt on one vignette among all. I measure result for entire topic on avr basis (all solved vignettes within topic) in this phase. Usually I try to solve at least 4-5 vignettes by 1 attempt in each topic.
Since there are also vignettes in almost each topic which I am able to solve stable on 83 % or 100 %, I am not worried about below average result on certain vignette. It’s just telling me in which area I still have poor performace. During next 30 days I will dedicate study to cover those areas. I plan to take first mock latest on 20th April.
I prepared MS Excel spreadsheet for performace measuring. It contains: result, solving time, then average, mode, median etc. in cummulative and performance by topic. So I am able to track my progress.