Automatic update in conversations doesn't fetch all of the posts

On PleromaFE commit 9e2fa50b

Steps to reproduce:

1. Open an active conversation with several participants
2. Wait for a reply to come in that automatically updates the conversation view
3. Check what that reply is replying to

Sometimes the post that the reply is replying to isn't on the conversation view, even though it should be. Closing and expanding the conversation again causes the missing post to appear normally.