Should I keep hopes up for an offer?

I am in the 3rd and final round for a tier2 consulting company, which consists of 4 interviews (2 principals, 2 partners) and one test. I am done with the test and yesterday I had the first 2 interviews, with principals. Overall, by the end of the whole process, I will have conducted 8 interviews + one test.
I feel quite nervous because in both cases from yesterday I made one wrong assumption in the analysis part, which were however pointed out after we were done with the whole case.
In the first interview, there were three processes out of which I was supposed to say which one would save the most costs, and then calculate those costs. I briefly explained my thoughts and said it is process A, the interviewer nodded, said he agreed and let me do the calculations. After the recommendation, he told me that "the reason why I give this case is because 90% of the candidates go for process A, like you did, however if you actually do the calculations for every process in advance you see that it is process B". His explanation afterwards made sense, but was rather counter-intuitive in my opinion, and I assumed that it would take too much time to do this (especially since we went 5+ min overtime).
In the second interview, the analysis part was about calculating a profit increase. At a specific point, I explained that we could either go with asking for the costs per unit or for the margins, and I asked for the margins. He gave them to me, and we ran the calculations without him pointing me on any errors. After we were done with the analysis part, the interviewer kept asking about and hinting on a part of my analysis approach. It took me long to figure out what he meant, but I finally realized and told him that I wrongly assumed that the margins were constant, which had led me to wrong numbers.
I feel bad about both of my wrong assumptions, but it also feels a bit strange to me that the interviewers did not give me a chance to give it a second thought and recover from my errors during the case, and instead let me do calculations with wrong assumptions... Especially because during both analyses parts I first walked them through my approach and then put in the numbers and did calculations, assuming that if anything was wrong with my approach they would have pointed it out. Instead, they were nodding and said "yes, I agree".
Especially in the second case, I explicitly said at the beginning that we could either go by costs/unit or margins, and I randomly asked first for data on the margins instead of data on costs/unit. If it were the other way around, he would simply have given me the costs and this issue would not appear at all.
Overall, besides these wrong assumptions, I feel that all the other parts were good to very good, means the interviewers seemed to like my initial structure and the overall flow of the case converstation, I made no calculation errors and, especially in the second interview, we had a great connection during the personal fit part.
I have two more interviews, with partners, tomorrow. One principal told me that the partner interviews would not really be "interviews", but "rather open conversations, they will probably not even give you a case" (idk what he meant tbh).
Are my chances now close to 0 because I made these two wrong assumptions in the analyses? I still have two partner interviews, but I am afraid that, if these are indeed more open conversations without a case, I won't have another chance to do well in the case analysis part. So my fears are that, no matter how well it goes, the four will sit together, the principals will point out my errors and I will be kicked out.
On the other hand, although the four allegedly will only make a decision unanimously, wouldn't they have informed me that they would not proceed with the two other interviews anymore if it was a deal breaker, given how valuable the time of two partners is (especially in a very small office of 30 people)?