BandMergeOp. Error message: "Product is not compatible to master product."

Edit: This issue has been resolved. I was using the BandMerge op instead of TOPSAR-Merge.

Since today, every time I try to merge coregistered Sentinel-1 subswaths using the BandMergeOp, I get this error message:

Product is not compatible to master product.

which corresponds to the exception thrown by the validateSourceProducts() method in

This works fine in older versions of SNAP.