Definitely possible, if one SAC is all it took to bum out on 40+...well then it'd be a tough gig.
At the moment, even if you're at a low rank you still have multiple SACs in order to increase your rank. If you sit down with your teacher and see where you went wrong and then improve on those areas, then I see no reason as to why you couldn't. Your main focus should be eliminating your areas of weakness and being holistically strong. Going into your next few SACs - especially the application tasks - if you can perform much better, the chances are you'll propel yourself in ranking. Ultimately, if you get a high enough rank and beast the exam (e.g. 39/40 and 78/80) then you're going to probably do very well.
I'm just going to address this to the whole forum because so many similar questions are coming up. One SAC is not going to destroy your chances of 40+, I know plenty of students who had low ranks after the first few sacs and then started ascending in ranking after working harder and smarter. They got amazing scores (45+ raw). I'm not saying you should do this, but I heard of a student who was getting consistent C+'s on their SACs and pulled a 50 - but, I should mention that the said student was spamming practice exams for a long time and was in a very strong cohort. Although this may be a myth, it really goes to show that anything is possible. You have to ask yourself: "If SACs mattered so much, that a 4% SAC could be the difference between 45 and 30, then what's the point of the exam"? I know the example is extreme but really, every person walks into the exam at a even playing field (if you forget about ranks).
I see this every year in VCE students and felt it a lot with friends in Year 12. The struggle you're feeling, is the same struggle 50,000 other students are feeling in the state. Put it into perspective, doing badly in a sac or two does not correlate to an assured <40 study score.