IB Replacement is creating new subline on a Entered Service Contract

We just upgrade from 11.5.10 to 12.1.3. We do IB replacements by creating Sales order. So in 11.5.10, if service contract is in Entered status, IB replacement would just flip the IB on the covered product. However when we ran the same process in 12.1.3, it showing two sublines, one wth status cancled and added new line with status entered. Also both sublines are referening to newly created IB??

So my question is why it cancelled the subline if line is in entered status as it was not happening in 11.5.10 and still showing newly created IB?

Thanks
Ravendra