TOPSAR Merge output

Hello everyone.
I am currently trying to merge two coregistered and debursted stacks of the subwaths IW1 and IW2. The output should be one stack of 7 images with the two subswaths stuck together.
However the merged stack has 7 images, but for just two of them (master and one slave) the subswaths became one. For the other images I only get the subswath IW1. It seems that TOPSAR Merge only worked for two images.

Did anyone face the same problem?