I’m guessing you haven’t provided the same Routing config to the browser? The browser is probably connecting and expecting the normal 8 responses to requests, but the network is only providing 2 (or whatever you set the min_section_size to for the vaults)
If you copy the safe_vault.routing.config file to the folder where your browser binary is, then rename it to match the binary (probably to safe-browser.routing.config) that should hopefully fix this for you 
You don’t need to copy the safe_vault.vault.config by the way, just the routing one.