libxpertmasscore-dev is declared Multi-Arch: same, but fails to
coinstall.

The file /usr/include/MsXpS/libXpertMassCore/config.h is shared by
libxpertmasscore-dev version 1.17.1-1 as present in forky and version
1.17.2-1 as present in unstable with varying content.

Please ensure that shared files have bit-identical content across
architectures, move architecture-dependent files to
architecture-dependent paths or remove the Multi-Arch: same field.

Kind regards

Helmut Grohne