Hello! I have had an M400 for 7 years and it has worked beautifully and we love it. Recently it stopped moving after 2-3 min in the pool. I took it to an authorized repair place and they said they could find no issues and it worked well on their end. Brought it home yesterday and same problem. Two questions. 1. Has anyone had this happen and any idea what it could be? 2. What should I buy to replace this unit? Open to suggestions but would love it to work as well as M400, for as long as possible and under $2k. Thank you!!