Unable to delink Employee Record from an old AD account

Hi Gurus,

Fairly new here so please be kind with my terminologies. In our OIM, we have HR Personnel information coming from Oracle eBusiness Suite (EBS)

A certain personnel was turned from Contractor to Full time employee, and hence a new AD account was required (as per our policies).

For some reason, AD account didn't get created during regular SYNC and someone ended up creating it manually.

We are now not able disconnect this users' Employee Record (linked to EBS Record) from his old AD Account.

Basically, in the Employee Record, we see Central Account is linked to his old AD Account. We want it to be linked to his new AD account (created manually).

Would you have any suggestions from a similar experience?