Upgrade task (MigrateGroupsToCwdGroups) requires cru_ps_group to be collated case-sensitive.
Without ensuring that migrating database has proper collation set, it is possible to drop all group associations in permission schemes silently, without any warning.
For reference, there is a query, which causes problems if fields have case non-sensitive collation: com/cenqua/crucible/hibernate/upgrade/crowd/MigrateGroupsToCwdGroups.java:112

// permission scheme
executeUpdate(conn, "DELETE FROM cru_ps_group WHERE cru_pid = ?", normalizedNewName);
executeUpdate(conn, "UPDATE cru_ps_group SET cru_pid = ? WHERE cru_pid = ?", normalizedNewName, oldName);