Hello,
As you may know, latest oppo devices using encrypted, even the newest one using encrypted and signed one.
Like Oppo A71, A83, F3, F5, F7 and devices after that.
So backup for this kind of secure imei is mandatory.
UFi current software release only support repair encrypted imei until Oppo A71.
So, there are no solution for your problem at the moment.
Hope soon will find solutions to this.
B.R