Thanks for openly sharing your situation - I am sure many candidates are in a similar position and can actually benefit from your thread!
Well - case interviews is neither rocket science nor brain surgery, and in hardly any other firms you have such extensive knowledge and transparency about exact recruitment process and requirements - so definitely it can be done well.
However - your situation also looks like a very common situation of several previous coaching candidates of myself. For sure quantity matters to immerse yourself into this case interview world. BUT: quality first! Just having done 200 cases (which is really a lot, I need to say!) does not mean you fixed fundamental issues or did some last fine-tuning - and I have had many many candidates who received great feedback from other coaches and were thinking that they were ready for real interviews - until we had our first coaching session in which I confronted them with a real-life case scenario and toughness of a real interviewer.
So - from my perspective you should evaluate first if that was more quantity than quality prep, and if your really had appropriate coaches and systematically covered all your weak spots and improved that over time!
Hope this helps - if so, please be so kind and give it a thumbs-up with the green upvote button below!