This appears to hit a corner case with respect to multiarch, in that changing a package from Multi-Arch: same / Arch: any to Multi-Arch: no / Arch: all is not handled cleanly on upgrade.
As libkadm5srv-mit8 appears to now be a transitional package, the correct solution here would appear to be to make it Arch: any / Multi-Arch: same again.
This appears to hit a corner case with respect to multiarch, in that changing a package from Multi-Arch: same / Arch: any to Multi-Arch: no / Arch: all is not handled cleanly on upgrade.
As libkadm5srv-mit8 appears to now be a transitional package, the correct solution here would appear to be to make it Arch: any / Multi-Arch: same again.