Hi binNMU are known to not work on the signing side of the archive.
dpkg contains special handling for binNMU style versions. If it sees a 1-1+b1 as version, it will search some source files with version 1-1. This means you can never properly have a source package with such a version. As the signing stuff just munges packages together and then calls dpkg stuff on it, the resulting files will show up in the wrong location and the whole thing errors out. The internal state tells that signing failed and will not be retried: | id | 4958 | ts | 2024-03-28 12:50:25.021108 | template_package_name | grub-efi-amd64-signed-template | template_package_version | 2.12-1+b1 | state | failed | error_msg | Command '['dpkg-genchanges', '-S', '-DDistribution=sid', '-UCloses', '-O../grub-efi-amd64-signed_1+2.12+1+b1_source.changes']' returned non-zero exit status 255. | suite_codename | sid | architecture | amd64 Bastian -- "Get back to your stations!" "We're beaming down to the planet, sir." -- Kirk and Mr. Leslie, "This Side of Paradise", stardate 3417.3