Comment 2 for bug 2132116

This may have been another occurrence.

automake 1:1.18.1-2 migrated on 2025-11-01, and was removed from -proposed
https://launchpad.net/ubuntu/+source/automake/1:1.18.1-2

and for several hours, many builds failed against the old automake 1:1.17-4ubuntu1 found in -release
https://launchpad.net/ubuntu/+source/automake-1.17/1:1.17-4ubuntu1

fortunately, these builds only needed retrying after the new automake was published and available in -release