The zypper refresh makes no difference. I verified that the delta rpm is valid:

Code:
# applydeltarpm -r noarch/my-aix-99.0.0-125.noarch.rpm drpms/my-aix-99.0.0-125_99.0.0-126.noarch.drpm 126.rpm
# cmp 126.rpm ../tmp/my-aix-99.0.0-126.noarch.rpm
#
I've studied the /var/log/zypper.log and found no errors or warnings.

The repo is a local repo, not an http repo, if that matters.