Someone more experienced with Vino and Nano may better advise.
My only ideas so far would be:
- Check encryption is disabled for Vino server.
- Try wired ethernet. Wifi errors may give such problems. You would check /var/log/syslog on Nano for wifi errors. If some are logged, you may check the wifi interface addresses and config, and/or change channel.
- If wired ethernet is not better, you may try another virtual desktop such as NoMachine.