Which posts disappear? It could be that the authors outbox relays are offline (lots of relays have been offline today) and Amethyst doesn't check other centralized relays for the posts. Wisp does. So it's probably case by case. If you can see one that doesn't show up on Amethyst, let me know..

Also, check if the amethyst is connecting many relays, sometimes Tor is offline and then only trusted relays will be used by default.