Sometimes missions offered by the Fahrelen fail to initiate properly, producing on-screen error messages:

10/04/2017 00:19:32 OnCreate [Defend Migration Route]: Unknown function [intPermutePairs] ### (@ thePair 0) ###
10/04/2017 00:19:58 OnMigrationArrived [Defend Migration Route]: Unknown ship class ID [Nil] ### (sysCreateShip (@ speciesData "leaderType") startObj (@ speciesData "sovereign") 3213738) ###