Gateway Imploded Because There Was Not Enough Space To Spawn The Next Wave
This is the most common "hidden" cause. Many gateways (especially those from the Apotheosis mod) are hardcoded to spawn mobs that only exist in certain dimensions. If you try to open a "Sunlit Ascent" gateway in a Mining Dimension or a void world, it may implode because the game cannot find valid "invaders" for that specific dimension.
if not has_enough_space(spawn_points, wave_units): delay_wave() or clear_old_units() This is the most common "hidden" cause