I previously had a MR number and a SPG number. When I tried to merge from the Marriott site, the process would stall. I then tried to merge from the SPG site and was successful (but also now have a new MR number replacing my SPG number like you.) You would think regardless of how you merged, it would just link each together but apparently they want to manage 3 numbers for me (old SPG, old MR, new combined)?