While flying the barge in hud view those small mining rocks (I believe that those are the reason) who are all around places will turn the barge nose upwards without beeing able to counter this effect besides changing hud view to third person. It happens a lot while flying through Omega 3 for example. It feels like a npc ship trying to turn it at it's tail although there is no npc ship around.
Though to clarify - That issue as a whole (large ships gettin bumped around by small asteroids) isn't fixed, and unfortunately I don't think it's even somethin we can reliably fix, but there was an issue that got in with this patch which was making it happen unusually too often with the Barge specifically - That is fixed. So it can still happen, but far less frequently (as frequently as any other large ship).