getAuthorFeed not returning all posts

[Bossett]

Describe the bug

getAuthorFeed is not returning all posts for at least one user:

getAuthorFeed for https://bsky.app/profile/did:plc:xwzxgbwvnnu2dntpty765y5j is not returning all posts - e.g. https://public.api.bsky.app/xrpc/app.bsky.feed.getAuthorFeed?actor=did:plc:xwzxgbwvnnu2dntpty765y5j&limit=100&filter=posts_with_replies&cursor=2024-06-28T02:59:07.446Z has no next cursor, however a search for that user turns up posts from well before the end of that feed.

To Reproduce

Steps to reproduce the behavior:

1. scroll to the end of https://bsky.app/profile/did:plc:xwzxgbwvnnu2dntpty765y5j until 'end of feed'
2. compare that result to https://bsky.social/xrpc/com.atproto.repo.listRecords?repo=did:plc:xwzxgbwvnnu2dntpty765y5j&collection=app.bsky.feed.post which has posts from much older if you follow the cursor

Expected behavior

getAuthorFeed should return all posts before returning a nil cursor

[bnewbold]

This is doing something weird in-app for me as well, can't consistently scroll on the replies tab, but can scroll much further on the main posts tab. Might be specific to posts_with_replies filter?

Totally speculating, but one thing that jumps out are a lot of reposts. Might have a full dataplane page of non-posts filtered out, resulting in an empty page of appview endpoint API results? Similar to old bugs with filtered posts in search results.

cc: @ericvolp12