chromium is historically bad with proxies. In this case I'd try to disable dot (secure dns) in the vanadium config. 
Also be sure you are running orbot in vpn mode (with "advanced mode" disabled, cause as I'm aware vanadium has no proxy integration, you need to route traffic trough android vpn. 
Another check you could do is see if orbot is setted as "vpn always on", it could prevent ip leaks in some cases