Constant disconnects when joining instance or minimizing

Do you alt-tab while changing instances? Is this only a disconnection? Or is there a client crash here aswell?

You're welcome to check that your Firewall/Antivirus programs are not interfering with Path of Exile's connectivity, using a wired connection to your modem/router, turning off any other programs while you play PoE and toning down some in-game display options. Feel free to provide as much information as you can about your system aswell, as this can provide the forum more information to diagnose your issue.