This sounds like the normal process. When code is flashed to bluz, the device needs to reboot so the code can be copied over to the application space. This will cause it to disconnect from your iPhone.
Our iOS app doesn’t automatically reconnect, but there is an option to allow it to do so. You need to go to the iOS Settings menu and then scroll down to the list of apps and look for the bluz app. Click on that and you will see a menu of options you can enable, including the ability to automatically reconnect to bluz devices. This would then reconnect bluz automatically after you flash code.
Let me know if that answers your questions.