On April 6, 343 Industries released the latest Halo 5 update, Ghosts of Meridian. Unfortunately, the update introduced a bug into custom games that renders Grifball unplayable.
As far as players have been able to determine, the bug impacts custom games where more than four players are present. The fifth through eighth players are unaffected by the gametype settings. For example, in Grifball, the first four players will spawn with shields, health, grenades, and speed as dictated by the custom game settings. The other four players will spawn with shield, health, grenade, and speed settings that are different.
You can see an example here, in a “practice” custom game with Grifball settings. One player even spawns with grenades.
343 Industries has been made aware of the problem and are working on a fix.
If you are playing in the current Grifball season, please postpone your games until the game is patched. Depending on how long it takes before the issue is fixed, we may extend the GGL regular season.