This has always been "my" worst nightmare with resale. I always buy same UY and title the same. I still always worry that Disney would mess it up.
I know in the end it's not a HUGE deal. However, since I plan to have my multiple contracts for the next 30+ years I would only want them to be under the same member account.
Heck I would even sell a contract if Disney couldn't fix it.
Over 30 years a small inconvenience adds up "for me".
PS. Are you sure its a different member number and not just a different contract number? Do you have to select what member from drop down to switch? Or do you see both contracts when booking with just ".1" difference?