MIM Software Algorithm Research Engineer interview questions

The interview started with two rounds of conversations with non-technical interviewers (a phone interview followed by a zoom call). Upon completing those I was given a problem to research and present a possible solution. I won't go into specifics, but the problem was related to medical image processing and was focused on the machine learning and/or applied math that could be used to come up with a solution. I submitted a thorough report with a solution that I believed was at least sufficient, and after about a week I was invited to participate in another video call interview with two research engineers. This portion of the interview was very technical, and I was asked to describe in detail how my solution might be implemented, including the underlying mathematical concepts, specifics of how input data should be prepared for the model, how the model should be trained, and ways to make the whole system more efficient. I had a decent handle on some of these concepts but my linear algebra knowledge was somewhat limited (I believe this is what kept me from receiving an offer).