Just a thought and admittedly it is 45 yrs since I sat ATPL.
It used to be a speed/accuracy exam and it was impossible to answer all the questions completely accurately. One therefore had to know where one had to be accurate and where one could make a quick calculation. This therefore demonstrated one knew where one had to be accurate and where one did not.
Could this be your problem ?
When I sat Flt Planning, I wrongly used G/S instead of TAS for a major calculation and did not discover this until much further into the question which was about 30% of the marks.
I left the calculations as was and wrote a note at side of calculations explaining the error and what I should have done. Ended up with mark of 93%, so few if any marks were deducted.
Also our lecturer knew the examiner at the time and said he had been told that a lot of examinees lost marks because the examiner could not follow the calculations made to answer the question.
So..very important...make your calculations readable and explain what you are calculating. H I H.
Emeritus