Something is fishy with byte arrays on big endian systems
containers 0.6.2.1 release (which introduced byte arrays usage into
Data.Graph and is shipped with GHC 8.6 and later) seems to have uncovered some endianness issues on big enidan systems (S390x and PowerPC).
For those affected by this issue there is a patch to disable unboxed array usage in
containers which can be used to workaround the issue until it is fixed.