Why didn't form phase information after coregistration?

data:terrasar images( beam-dimap)
At first,everything is ok.While I processed the data using coregistration twice. The phase information is lost.I tried in st1bx but falied.The intensity formation is still there.I don’t know why.

i and q has the phase information. You only need a phase band after generating the interferogram.

Maybe the phase information have always been the consequence after coregistration which could be opened as a image before.If it did not have an impact on generating the interferogram.Everything is ok.