Dyson Process Chemist interview questions

Very long process. Applied for the job mid July. They removed the job offer and reposted a few days later at the end of July, August, and September. I forgot about the application when they contacted me in October for a phone interview. The interview went well and I was invited for an interview at the HQ in Malmesbury. The interview was in two parts, an HR one first and then a technical one. Think about all the boring questions they could ask, I had them and twice as the technical manager felt compelled to ask the same question the hr person asked me half an hour before. On the technical questions, they would ask very vague questions like how would you improve a process? We cannot give you any details what we do is super secret, but when you give a vague answer they would ask you to be very specific. I sent a thank you email the next day and follow-up emails after a couple of weeks asking for an update and some feedback. They didn't even bother answering.