I didn't see this on the forum as being discussed previously, so I thought I would bring this up. When people leave or get removed from the guild, I've noticed that their guild_id gets changed to 0 in table roster_members as it should. However, in table roster_players the guild_id stays the same.

Shouldn't the guild_id be updated in roster_players as well?

Yes and no
In fact, it shouldn't be set to 0 at all, it should be set to the current guildless id for that region-realm

The original idea was to set it to 0, but that doesn't work well to merge all the guildless members of a realm for use

So we switched to adding guildless guild_ids to work around this issue, but we didn't change the code that detects and tags members for this, it still sets them to 0

So what now?
This means that Roster is setting/removing members incorrectly, and we still need to fix it