“A Symmetry of Imperfection” is episode nineteen of season four of Andromeda.
The Andromeda Ascendant is orbiting a planet whilst Beka takes a team of redshirts (okay, they aren’t wearing red, but they fulfil the same role) down to the surface. The occupants are missing, and they discover why when Magog attack – evolved Magog.
Dylan goes down to the surface with Trance to help, and a huge Magog ship, described as a satellite ship appears. In orbit, the Andromeda leaves. This causes problems when a fail safe program of Harper’s activates. The ship’s core AI decides that there are problems with Rommie, and shuts everything down until they can be sorted out. Which leads them dead in the water, and the Magog coming.