The Setup

The setup should be

• Computer A: Vault folder in dropbox folder + Obsidian Sync on
• Computer B, C, D: Vault folder in local file system (Not dropbox folder) + Obsidian sync

You want only one vault hosted from the dropbox folder itself, the other computer’s obsidian vault should be local folder and not dropbox because obsidian sync takes care of syncing and if dropbox tries to sync too, you get a bunch of errors and missing files (can be restored but troublesome).

Why

We want dropbox so

• we can access obsidian files from the web (in case you are on a computer where you don’t want to sync the entire vault)
• version history by dropbox is great as an extra backup option

We want obsidian sync as:

• it makes all syncing very smooth between computers and mobile (but very slow when loading changes)