as an alternative to the S1 TOPS Coregistration you can proceed as follows:
- S1 TOPS Split (select only the required bursts and VV polarization only), perform for both images individually.
- Apply Orbit file
- Coregistration (Radar > Coregistration > Coregistration)
- Interferogram generation
- TOPS Deburst
- Multi-Looking and Goldstein FIitering (optional)